Add documentation on how to write markdown

[astyled]

Describe the change you'd like:

Add good, compact, descriptive, user-friendly documentation for Markdown syntax used for the fields on the website.

Additional context:

Some draft from a proprietary Internet messaging platform can be used for inspiration or as a base for this.

[vednoc]

Could you use the one you made a while ago as the base for a PR?

[astyled]

no way i'm going to publish this crappy draft to github

Ok, fine..