Doesn't work with OffscreenCanvas

[delarre-reve]

When running pixi against an OffscreenCanvas rather than a regular Canvas (and particularly when running off the main thread entirely) the dev tools don't appear to work.

I think this is due to the Overlay functionality which is trying to measure the canvas with getBoundingClientRect and also does other DOM node creation which isn't accessible from a webworker.

Would be good to just disable this functionality when initialized with an OffscreenCanvas as a first step, but full support would also be nice though a more complicated fix.

[Zyie]

ahh ok, thanks for raising this, I will take a look!