Normalize digital media in Discogs searches

[sindreruud]

The Discogs plugin supports media as an extra_tags search filter and maps it to Discogs' format parameter.

Discogs uses the word File to describe digital releases. MusicBrainz on the other hand uses something different, Digital Media

If you have music previously tagged against MusicBrainz, the metadata will usually say Digital Media. I have also seen WEB being quite common.

As a result, enabling media in discogs.extra_tags can negatively impact the search accuracy, while in reality it should not.

This PR normalizes Digital Media and WEB to File when constructing the Discogs search filter.

PS, this is my first PR in this project. So please let me know if there is something I need to correct. I tried following all the documentation to the best of my knowledge.

• [✓] Documentation
• [✓] Changelog
• [✓] Tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.85%. Comparing base (a750105) to head (1be6d74).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6980   +/-   ##
=======================================
  Coverage   76.85%   76.85%           
=======================================
  Files         163      163           
  Lines       21627    21629    +2     
  Branches     3344     3345    +1     
=======================================
+ Hits        16621    16623    +2     
  Misses       4190     4190           
  Partials      816      816           

Files with missing lines	Coverage Δ
beetsplug/discogs/__init__.py	69.66% <100.00%> (+0.18%)	⬆️

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