Add option to render in a web worker

[jaredjj3]

Drawing the rendering is the most computationally expensive process, and it blocks the main thread. I think it's unacceptable for blocks O(100ms).

Investigate the possibilities of:

• rendering SVG in a web worker, then piping the raw SVG data back
• rendering canvas in an OffscreenCanvas, then transferring ownership to the main thread.

This would make rendering asynchronous, so we'll need to expose an appropriate API.

The main thing I'm unsure of is if this library needs some Web API that's not available in the web worker context.

[eliot-akira]

rendering SVG in a web worker

I was curious about this, and found a couple of useful links:

• MDN: Functions and Classes Available in Web Workers
• Wrangling SVGs without a DOM

The latter article describes using linkedom to provide DOM methods like createElement in a web worker.

[jaredjj3]

These look promising, thanks for finding them!