Controller mapping & new mechanic!

I'm done with controller implementation!

-You can now remap actions to controller buttons how you want, with the exception of movement staying on analog stick (it would require way too much work for what it's worth).

-Added a new sand block, a type of solid block through which your character can dash in straight line.

Also, I made a new level (not playable yet) that uses the sand blocks, and fixed the music playing its base volume for a short moment when launching the game before going back to its saved volume.

This new sand block and level are the start of a new biome, the sandy seafloor, that I'll be working on next. I'm so pumped to go back to producing actual content (I already coded 2 new enemies just for kicks).