Add a note to the changelog

Author: snejus

docs/changelog.rst

@@ -30,9 +30,16 @@ New features
     Bug fixes
     ~~~~~~~~~
 
-..
-    For plugin developers
-    ~~~~~~~~~~~~~~~~~~~~~
+For plugin developers
+~~~~~~~~~~~~~~~~~~~~~
+
+- Consumers of :py:class:`beetsplug._utils.musicbrainz.MusicBrainzAPI` now
+  receive normalized MusicBrainz payloads with underscore-separated field names
+  (for example ``artist_credit`` and ``release_group``) and grouped relation
+  lists such as ``work_relations``, ``release_relations``, and
+  ``url_relations``. The API responses are also now fully typed with concrete
+  ``TypedDict`` models for releases, recordings, works, and relations. Update
+  direct access to raw MusicBrainz response keys if needed.
 
 ..
     Other changes