Follow the HTML canvas specification and add missing
'setTransform(transform)' method to CanvasPattern interface.
https://html.spec.whatwg.org/multipage/#dom-canvaspattern-settransform
Testing: Improvements in the tests
- html/canvas/element/fill-and-stroke-styles/2d.pattern.transform*
- html/canvas/offscreen/fill-and-stroke-styles/2d.pattern.transform*
Signed-off-by: Andrei Volykhin <andrei.volykhin@gmail.com>