Suggestion: Node.js worker threads support

[ryardley]

Now that Node.js has worker threads available it would be great to be able to see rayon parallelism in that context. This would be especially helpful for testing wasm functions that might be deployed within a browser context with standard JS testing tools like jest or vitest as opposed to having to resort to using heavy handed techniques such as puppeteer.

Reference: https://nodejs.org/api/worker_threads.html

[RReverser]

Yeah I don't mind at all. It should be under a separate Cargo feature, since unfortunately Node API is different from browser one, but if you want to submit a PR, one would be very welcome.