Docs for the docs

[JorgeCastilloPrz]

Follow up to #1139 which was a very good start for the Ank docs.

Fixes #1195

• Add how to contribute section including all required details
• Add docs structure summary to help people having a mental map
• Added formatting guidelines
• Add prioritized policies on how to add snippets
• Add how to deploy Ank to a local server to test your changes

[JorgeCastilloPrz]

I'd love to get some eyes mostly in the section about snippet policies on when to go for Dokka inlined docs, runnable snippets, and other stuff. Let me know if it's clear and whether it's in the line of what we want to do with snippets @raulraja.

[pakoito]

I would add a section here that there needs to be a small description and a link from the datatype or typeclass intro pages back to the doc, so people can scan them easily in a single page.

[JorgeCastilloPrz]

Makes sense. Added now 👍

[raulraja]

Excellent and much needed, thanks

[pakoito]

To p'alanteeeerl