added fix-comment subcommand

move the spotify url from comments to own tag (spotify)

internal/metadata/vobis.go

@@ -183,5 +183,9 @@ func createVorbisMetaBlock(m Metadata) flacvorbis.MetaDataBlockVorbisComment {
 		vorbisMeta.Add("ALBUMARTIST", albumArtist)
 	}
 
+	if m.SpotifyID != nil {
+		vorbisMeta.Add("SPOTIFY", *m.SpotifyID)
+	}
+
 	return *vorbisMeta
 }