Add recommended prior knowledge of users to prerequisites // provide links for research about mailcow-dockerized-docs

[seniorm0ment]

Some ideas:

• Basic UNIX based system administration, security, and management
  • Basic navigation and tools of UNIX based operating systems ( ls, cd, vi, etc.)
  • Basic usage of UNIX based CLI tools, especially networking ones such as ping, dig/drill/nslookup, etc
  • Basic UNIX based server security such as SSH key management

the RHEL docs can be decent for some of these topics, for example security:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html-single/security_guide/index

• Basic Docker/Docker-compose knowledge

• Basic networking understanding, and ideally experience with DNS records.

• Safeguarding, Backups, Restores

I'd be willing to help throw in some information when the actual documentation page is created.