This is a first pass at implementing CRC2D.createPattern() and the
associated CanvasPattern object. This implementation only works for a
few of the required image sources [like CRC2D.drawImage()], and does
not yet support transforms. Other than that it supports everything
else (which is mainly the various repeat modes).
This gets:
- CanvasRenderingContext2D.createLinearGradient()
- CanvasRenderingContext2D.createConicGradient()
- CanvasRenderingContext2D.createRadialGradient()
Actually working as fill styles for paths and rectangles :^)
Getting them working for strokes is left as an exercise is
left as an exercise for the reader.
