How to add music to digital player:
0. Number of loaded audio files XX is determined in Special Option (Max is 30)
1. Create music_01.sdef to music_XX.sdef by copying _example.sdef
2. use notepad++ to open each sdef, and change the music name (music_01, ..., music_10)
   Note: no appendix name
3. Go to JF-17/Sounds/Effects/DPlayer/
4. Put your music_01 to music_XX (ogg or wav) there
