Simplify installation of needed utilities a lot about sops-nix

[Mic92]

ssh-to-pgp will be easier to install after NixOS/nixpkgs#111543

[Mic92]

How about adding this line?

$(nix-build --no-out-link 'https://github.com/Mic92/sops-nix/archive/master.tar.gz' -A ssh-to-pgp)/bin/ssh-to-pgp --help
Usage of /nix/store/k3jdkarw9dvary3xabv407igapc349kc-ssh-to-pgp-0.0.1/bin/ssh-to-pgp:
  -format string
        GPG format encoding (binary|armor) (default "armor")
  -i string
        Input path. Reads by default from standard output (default "-")
  -o string
        Output path. Prints by default to standard output (default "-")
  -private-key
        Export private key instead of public key

does not even require to install it.

[Mic92]

Is this easier to follow? #57

[Mic92]

sops-pgp-hook is still not easy to install. I am thinking about changing the way this part works too.

[ebbertd]

Is this easier to follow? #57

Yes it is. Thank you very much!

[Mic92]

README now has a example shell.nix that makes installation easier.