run the wasm component in web worker

[mustafa0x]

to avoid blocking the main thread. this should be done for the webcomponent first: https://github.com/DigitalKhatt/digitalkhatt.org/tree/master/examples/webcomponent

[mustafa0x]

update: this is blocked by https://github.com/DigitalKhatt/visualmetafont/blob/master/src/weblib/quranshaper.h#L200 QuranShaper::shapeText since it takes the canvas ctx, which can't be passed to the worker (error: "CanvasRenderingContext2D object could not be cloned").

edit: this can be perhaps worked around by using OffscreenCanvas, but no safari support in <16.4.