Game update made after gamejam ended (and as such will be added after rating time will end)

- Added music for main menu and credits;
- Added colliders missing on the level 3;
- Fixed colliders on the level 2;
- Scripts controlling the music have been changed, it now changes smoother and more reliably;
- Fixed bug that doubled music and ambiance on levels after restarting the game.

- Added Linux build (yet not tested)