Add Node support

[agilgur5]

I never quite wrote this down (until now), but for a while had been looking to add Node support somehow so that it supports most platforms and can work in testing frameworks etc.

worker_threads were released back in Node v10 and were the main thing I was considering. IIRC the API is a bit different and might require some changes, which is why I never quite implemented it.

Figured I'd finally make a space for jotting down notes about this