Enable worker_threads where available

[developit]

It would be nice to have this run in threads rather than child processes on versions of Node with worker_threads. Jest-worker supports automatically detecting and using threads, but as per the docs, will only do so when passed enableWorkerThreads:true:

jest-worker will automatically detect if worker_threads are available, but will not use them unless passed enableWorkerThreads: true.

[kherock]

+1

I'd really like to see this since it would allow me to bypass jestjs/jest#12060 which is preventing me from using Yarn's ESM loader with this plugin.