PR review on wildcard.media please

I'd like a review on https://github.com/collective/wildcard.media/pull/65 please
the bug I reported and trying to fix is https://github.com/collective/wildcard.media/issues/64

Bug: tl;dr - your twitter and og cards 'image' get replaced with your audio file.

PR: tl;dr - wildcard.media registered syndication adapters for it's new types. Makes sense for RSS but this is what breaks the twitter cards and such. Problem might be a bit bigger than just wildcard.media, but at least your twitter cards don't get borked on install anymore.