Feed rss can be improved

What is the problem you are facing?

RSS feed generated by funkwhale can be improved

What are the possible drawbacks or issues with the requested changes?

Nothing is bulletproff but this is just following the specs

Context

The feed RSS doesn't contain the schema xmlns:content

https://podcasters.apple.com/support/823-podcast-requirements

RSS feed URLs must adhere to RSS 2.0 specifications, be publicly addressable (not password-protected), and include the following XML declaration:

<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"    xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd"  xmlns:content="http://purl.org/rss/1.0/modules/content/">

I wouldn't mind making a MR, but I'm not sure if there are more places to implement than renderers.py and neither can I test right now.

There are other things to improve, but I would like to know first if this is the right channel to propose the options or if a Matrix channel is preferred for this kind of thing.