Mouse and keyboard examples

[nick-paul]

• Standard library
  • Wrap mouse & keyboard :{graphics.*} functions in canvas
• Examples
  • [new] Simple mouse input (canvas/mouse.aya)
  • [new] Color Typewriter (canvas/color_typewriter.aya)
  • [updated] Move attractor with mouse (canvas/attractor.aya)
• Bug fixes
  • Fix uncaught index error when setting index of list
  • Fix NullPointerException thrown when accessing canvas input before displaying the canvas