README.md files for Ansible plugins

The supplied plugins, like the callbacks and filters, have the potential to be a great resource.

Unfortunately, they are lacking standardised documentation which makes it difficult to understand their function and/or output without studying the code - not particularly scalable once there are many submissions.

The addition of a templated markdown README for complex plugins would make them much easier to browse and understand.

Would you accept PRs with READMEs for the plugins?

If so, would they move to a directory of the same name or sit in the same directory (side-by-side like the inventory scripts and associated .ini files).

On my wishlist I have an item to generate docs for ALL plugins like we
currently do for modules/task plugins, if we standardize on 'external'
rst or go again for an 'in module doc' is yet to be decided.

But at this point any docs are welcome.