Alpha 0.2.0

Player movement still isn't as fluid as it should be

Changes:

• Reworked player movement as a state machine
• Implemented dash
  • the player can press shift when moving left or right to briefly move a lot faster, ignoring gravity
  • the player can only dash horizontally
  • when dashing into a slope, the dash is redirected to follow the slope and the duration is refreshed
• Reworked how walljumping is handled
• Added an icon for the game window (executable icon pending)
• miscellaneous tweaks to the code and player movement

Full Changelog: v0.1.2-alpha...v0.2.0-alpha