Improved documentation for Podcasting 2.0

Is your feature request related to a problem? Please describe

We should crowdsource more details on how to further improve podcasting 2.0 support within Castopod

Describe the solution you'd like

• Clearer documentation on exactly what is and is not supported
• How to add functionality through rss tags
• Anything else (please mention in comments).

Describe alternatives you've considered

Learning more about rss tags, but still needs documentation on Castopod end.

Additional context

Thanks for considering!