cavestory save lib

modify major values in CaveStory(plus)'s profile.dat

Note

As impl From ... in src/items/*.rs, if you get invalid value from profile.dat, it will set to None(Nothing for BGM).

TODO

• [ ] Teleporter
• [ ] equipments - currently not in plan, since inventory provides options for equipments
• [ ] flags (bitvec) - currently not in plan, as modify this may break game experience