Touhou Mugakudan 3 song update. (#2659)

- Adds all the songs from the Touhou Mugakudan -Ⅲ- update. 
- Increases the upper limit of additional songs to 508 due to there being 512 songs now.
- Finally fixes umpopoff. As it was the only song that had less than 3 difficulties but also didn't have proper difficulty values

worlds/musedash/__init__.py

@@ -328,5 +328,6 @@ class MuseDashWorld(World):
             "victoryLocation": self.victory_song_name,
             "deathLink": self.options.death_link.value,
             "musicSheetWinCount": self.get_music_sheet_win_count(),
-            "gradeNeeded": self.options.grade_needed.value
+            "gradeNeeded": self.options.grade_needed.value,
+            "hasFiller": True,
         }