Add support for the "podcast" namespace

[ibz]

The "podcast" namespace is getting quite some traction these days. It would be awesome to be able to properly parse feeds that use this namespace.

Details about the "podcast" namespace: https://github.com/Podcastindex-org/podcast-namespace
1.0 spec: https://github.com/Podcastindex-org/podcast-namespace/blob/main/docs/1.0.md

More specifically, I am trying to parse the podcast:valueRecipient tags and I took this feed as an example: http://feed.nashownotes.com/rss.xml

What happened was: only the last of the 5 recipients is accessible in the parsed feed (under ['feed']['podcast_valuerecipient']).

I'm happy to look into this, but it seems like adding new namespaces is non-trivial and I don't see any tutorials on how to do it, so I guess I would just have to see how other namespaces are implemented and try doing the same - right?

Before that - is there some quick fix through which I could possibly access all tags of an unknown/unsupported namespace in the parsed feed?

Cheers!

[ibz]

Could this be related to this BTW? #297

I think support for the "podcast" namespace would be still nice, and I am willing to spend a little time to look into it, but the fact that multiple tags become inaccessible seems like a more general issue.