Add more guidelines how to contribute to documentation

[sboldyreva]

To ease the process of contributing to AlmaLinux Documentation and keep it the same style, it would be nice to have style guides listing and describing existing standards.

Example of the guidelines to collaborate on: https://github.com/AlmaLinux/wiki/pull/359

[sboldyreva]

@bennyvasquez @codyro @jonathanspw @xsub @andrewlukoshko

[sboldyreva]

closing as #359 got merged