Add support for Media Extension

[chrisppy]

The specification is located here

[azmeuk]

For the record, Media-RSS is used by youtube in their feeds.

[thedanhoffman]

I would like this as well, or at least the option to specify arbitrary strings

[Qwertie-]

This would be nice. I had a quick look in it and its quite a chunk of work to get done though as the spec includes a whole lot of flexibility and annoying logic with multiple ways to specify metadata.

[a-chacon]

Hi! Is there a workaround for this? I need to get a media::content tag from an item. I'm currently using this crate.

[andy128k]

@a-chacon While there is no first-class support for a media extension in the crate (PRs are welcome, BTW), there is still a way to consume any arbitrary tags. See an example.

[a-chacon]

@andy128k thank you! It solved my problem! is not the optimal solution but works for now