Backport dummy canvas APIs

[nikneym]

This is missing getContext method since I'm not sure how custom element methods are implemented in zigdom.

[karlseguin]

I don't understand how this is related to custom elements?

[nikneym]

I don't understand how this is related to custom elements?/

Sorry for the misunderstanding, what I was trying to mean is to provide getContext function to HTMLCanvasElement.

[karlseguin]

There's a fn getContext() in https://github.com/lightpanda-io/browser/blob/zigdom/src/browser/webapi/element/html/Canvas.zig. You can remove the dummy RenderingContext2D from that file. Remove the registerTypes function (since you're explicitly adding RenderingContext2D to the bridge)..and that's it.