readme.md: document metadata-prefer-id

readme.md

@@ -33,7 +33,6 @@ properties:
             description: >-
               Media that was originally available through the now-defunct nigge.rs online radio.
               Tagged items may contain the original _nigid and/or _nigkey as metadata
-
             $seeAlso:
             - '#/properties/songs/items/properties/metadata/properties/_nigid'
             - '#/properties/songs/items/properties/metadata/properties/_nigkey'
@@ -47,6 +46,11 @@ properties:
           - const: moonman
             description: 'Moonman songs'
 
+          - const: metadata-prefer-id
+            description: >-
+              Use the Media id instead of the metadata title for MediaSession.
+              Primarily for media where the source title does not match the assigned id
+
           - regex: '^radio\-media\-style\-[a-z\-]+'
             description: >-
               Used to add or remove styling for particular Media, such as to remove the