Player Control and UX fixes

Hey all, some things we'd been meaning to fix for a while. Felt it was finally time we did so. 

Player Controls Overhaul:

• Fixed bug that would cause player input to not register in certain circumstances
• Added coyote time
• Floor detection ray-cast now comes from both sides of player rather than only one from the center
• Player will now come to complete halt far faster (particularly after a jump) when left/right movement controls are released
• Player is now slightly less slippery overall
• Changed player collider from single circle to compound collider with two 'feet' - allowing player to be partially off platform without slipping off, but not feeling super rigid

Minor UX related level changes:

• Made the opening of the game slightly more forgiving
• Additional checkpoints 
• Added environmental cues to indicate where to go, particularly when backtracking / going left is necessary
• Changed some tile colours to better indicate places that cannot be accessed / fewer places where walls appear to be climbable
• Some puzzles were made slightly more intuitive / fewer leaps of faith are needed
• Smoothed over some single-tile jumping off points
• Tidied up some colour sections that were kinda ugly

Misc:

• Cursor is no longer visible while playing the game as executable