big update

I added a lot of features, amongst others there is now:
- a windows build that automatically saves your game (in the browser version you still can't save)
- music and sfx
- a combo-system (each subsequent move in a single turn increases in power)
- the "crush"-system (fill up the bar by clearing lines, when the bar is full you can "crush": press C to drop all energy in the field and clear a ton of lines in one go)
- bug fixes
- ...