OffscreenCanvas support in feature matrix

[juj]

Add item for OffscreenCanvas support in feature matrix, and update missing @requires_offscreen_canvas in browser test.

This will automatically set min browser versions when -sOFFSCREEN_CANVAS is used, and error our if the users explicitly requests a too-old browser version

[sbc100]

Doesn't only one of the variants require it?

[juj]

Yeah, that's right.

I thought to keep this change simple and over-conservative, to avoid too much churn from testing old browsers.

[sbc100]

Can you mention in the PR description what the effect this is, since I don't think its obvious.

Correct me if I'm wrong but something like: "This will automatically set min browser versions when -sOFFSCREEN_CANVAS is used, and error our if the users explictly requests a too-old browser version".

[juj]

Correct me if I'm wrong but something like: "This will automatically set min browser versions when -sOFFSCREEN_CANVAS is used, and error our if the users explictly requests a too-old browser version".

That's good. Added, thanks.