Fetch remixer field from Discogs

[ultram4rine]

Proposed solution

Discogs seems to show remixers. Example. In api schema it is in extraartists "role": "Remix"

Objective

Goals

Non-goals

Anti-goals

[ultram4rine]

BTW does remixer tag actually written to file? cause there is no such field in mediafile

[snejus]

I've recently added an issue in mediafile to support this field.

Meanwhile, I parse remixers from Discogs data in my fork. Seems like it's time cherry-pick this commit here!