Investigate optional OffScreenCanvas usage

[crutchcorn]

https://web.dev/articles/offscreen-canvas

Check to see if consistency is what we'd expect and if this gets better/worse

[evelynhathaway]

I am currently using node-vibrant in an application that uses OffScreenCanvas for an unrelated feature already, and I am considering refactoring my own usage of OffScreenCanvas to use a postMessage-transferrable ImageBitmap instead of a ImageData object that has to be structuredClone()'ed.

My application was already getting a performance uplift by using OffScreenCanvas with ImageData, and I imagine node-vibrant could get even more uplift by moving off the main thread if it doesn't have to deal with the performance penalty of loading an image on the main thread, converting it to ImageData, cloning it, and then transferring it.