GBC-spelunky v0.2.1

Heyo, it's been a while, but I finally decided to go back and squash the last few bugs I could find in this project!
Here is a full changelog:

• Fixed a bug related to a bugfix in the previous version, woops
• All VRAM access is now safe
• Fixed a game crash when going to a new level
• Made sure HDMA isn't started during Hblank
• Added/changed some documentation here and there'

That's pretty much it, have fun :)
-sukus