Feature Proposal: Web Worker support/example

[qrohlf]

I'd like to run some tests on how to move Trianglify computations off the main thread.

The main use case here is increasing the responsiveness of the sliders on https://trianglify.io/ - normally, for high-framerate use cases I would recommend implementing custom animation logic on the raw geometry output of Trianglify, but because the input sliders require mesh re-generation and re-coloring this is a unique situation that means I have to call the full trianglify().toCanvas() pipeline every time the user moves a slider.

Throttling to 15fps and/or using requestAnimationFrame can help in some situations, but ultimately moving pattern computation off the UI thread would be the most effective solution to this problem.