Add bash/zsh auto-complete capabilities about wordfence-cli

[akenion]

Auto-complete is implemented specifically for bash at present (though the Python script that backs it is portable).

This can be used directly in zsh as well by running the following before sourcing the bash completion file:

autoload -Uz +X compinit && compinit
autoload -Uz +X bashcompinit && bashcompinit

[davidnuzik]

v2.1.0-rc2 11/27/23

SUMMARY:
QA validation PASSED. Auto-completion works for me after testing on a couple of different environments. I tested primarily with bash and briefly with zsh. Either seems to work as expected.

VALIDATION STEPS

1. Source the scripts/complete.bash file (such as by cloning the project or just by downloading this file).
2. Ensure that auto-complete works as expected for all the subcommands and args - I spot checked many of them but not every single one. When I would partially type a subcommand and then a - for an arg and then <TAB><TAB> to list all, then all args were printed from what I can tell, so everything should be good to go.
3. Test with each bash and zsh, note the extra steps for zsh Alex mentioned in this issue.

NOTES:
Example of ` autocomplete results for each subcommand

david@ubuntu2204:~$ source wordfence-cli/scripts/complete.bash 
david@ubuntu2204:~$ wordfence vuln-scan -
--accept-terms              -E                          -l                          --no-debug                  --output                    --quiet                     --smtp-user
--banner                    --email                     -L                          --no-help                   --output-columns            --read-stdin                -t
-c                          --email-from                --license                   --no-informational          --output-format             --relative-content-path     --theme-directory
-C                          --exclude-vulnerability     --log-level                 --no-output                 --output-headers            --relative-mu-plugins-path  -v
--cache                     -f                          -m                          --no-output-headers         --output-path               --relative-plugins-path     --verbose
--cache-directory           --feed                      -M                          --no-prefix-log-levels      -p                          --require-path              --version
--check-for-update          -h                          --no-accept-terms           --no-purge-cache            -P                          -s                          -w
--color                     --help                      --no-banner                 --no-quiet                  --path-separator            --sendmail-path             --wfi-url
--configuration             -i                          --noc1-url                  --no-read-stdin             --plugin-directory          --smtp-host                 --wordpress-path
-d                          -I                          --no-cache                  --no-require-path           --prefix-log-levels         --smtp-password             
--debug                     --include-vulnerability     --no-check-for-update       --no-verbose                --purge-cache               --smtp-port                 
-e                          --informational             --no-color                  --no-version                -q                          --smtp-tls-mode             
david@ubuntu2204:~$ wordfence malware-scan -
-a                       --debug                  --images                 -n                       --no-include-all-files   --output-columns         -s                       --wfi-url
--accept-terms           -e                       --include-all-files      -N                       --no-match-all           --output-format          --scanned-content-limit  --workers
--allow-io-errors        -E                       --include-files          --no-accept-terms        --no-output              --output-headers         --sendmail-path          -x
--banner                 --email                  --include-files-pattern  --no-allow-io-errors     --no-output-headers      --output-path            --smtp-host              -X
-c                       --email-from             --include-signatures     --no-banner              --no-prefix-log-levels   --pcre-backtrack-limit   --smtp-password          -z
--cache                  --exclude-files          -l                       --noc1-url               --no-progress            --pcre-recursion-limit   --smtp-port              
--cache-directory        --exclude-files-pattern  -L                       --no-cache               --no-purge-cache         --prefix-log-levels      --smtp-tls-mode          
--check-for-update       --exclude-signatures     --license                --no-check-for-update    --no-quiet               --progress               --smtp-user              
--chunk-size             --file-list-separator    --log-level              --no-color               --no-read-stdin          --purge-cache            -v                       
--color                  -h                       -m                       --no-debug               --no-verbose             -q                       --verbose                
--configuration          --help                   -M                       --no-help                --no-version             --quiet                  --version                
-d                       -i                       --match-all              --no-images              --output                 --read-stdin             -w                       
david@ubuntu2204:~$ wordfence configure -
--accept-terms          -d                      --help                  --no-cache              --no-purge-cache        --purge-cache           --smtp-port             --workers
--banner                -D                      -l                      --no-check-for-update   --no-quiet              -q                      --smtp-tls-mode         
-c                      --debug                 -L                      --no-color              --no-request-license    --quiet                 --smtp-user             
--cache                 --default               --license               --no-debug              --no-verbose            -r                      -v                      
--cache-directory       -E                      --log-level             --no-default            --no-version            --request-license       --verbose               
--check-for-update      --email                 --no-accept-terms       --no-help               -o                      --sendmail-path         --version               
--color                 --email-from            --no-banner             --no-overwrite          --overwrite             --smtp-host             -w                      
--configuration         -h                      --noc1-url              --no-prefix-log-levels  --prefix-log-levels     --smtp-password         --wfi-url               
david@ubuntu2204:~$ wordfence terms -
--accept-terms          --color                 --email-from            --log-level             --no-color              --no-verbose            --sendmail-path         -v
--banner                --configuration         -h                      --no-accept-terms       --no-debug              --no-version            --smtp-host             --verbose
-c                      -d                      --help                  --no-banner             --no-help               --prefix-log-levels     --smtp-password         --version
--cache                 --debug                 -l                      --noc1-url              --no-prefix-log-levels  --purge-cache           --smtp-port             --wfi-url
--cache-directory       -E                      -L                      --no-cache              --no-purge-cache        -q                      --smtp-tls-mode         
--check-for-update      --email                 --license               --no-check-for-update   --no-quiet              --quiet                 --smtp-user             
david@ubuntu2204:~$ wordfence help -
--accept-terms          --color                 --email-from            --log-level             --no-color              --no-verbose            --sendmail-path         -v
--banner                --configuration         -h                      --no-accept-terms       --no-debug              --no-version            --smtp-host             --verbose
-c                      -d                      --help                  --no-banner             --no-help               --prefix-log-levels     --smtp-password         --version
--cache                 --debug                 -l                      --noc1-url              --no-prefix-log-levels  --purge-cache           --smtp-port             --wfi-url
--cache-directory       -E                      -L                      --no-cache              --no-purge-cache        -q                      --smtp-tls-mode         
--check-for-update      --email                 --license               --no-check-for-update   --no-quiet              --quiet                 --smtp-user             
david@ubuntu2204:~$ wordfence version -
--accept-terms          --color                 --email-from            --log-level             --no-color              --no-verbose            --sendmail-path         -v
--banner                --configuration         -h                      --no-accept-terms       --no-debug              --no-version            --smtp-host             --verbose
-c                      -d                      --help                  --no-banner             --no-help               --prefix-log-levels     --smtp-password         --version
--cache                 --debug                 -l                      --noc1-url              --no-prefix-log-levels  --purge-cache           --smtp-port             --wfi-url
--cache-directory       -E                      -L                      --no-cache              --no-purge-cache        -q                      --smtp-tls-mode         
--check-for-update      --email                 --license               --no-check-for-update   --no-quiet              --quiet                 --smtp-user  

Tested primarily on amd64 Ubuntu 22.04.3 with GNU bash 5.1.16, and zsh 5.8.1 -- both were provided by default ubuntu repos.