ability to disable the process hooks added by #150

[scottbessler]

I have my own graceful shutdown functionality, so would need to disable this functionality so I can control when process.exit is called as I have more to do than clean up worker threads.

At the very least, it would be useful to be able to disable this functionality. I do think its bad for a library to add calls to process.exit in general, and would encourage you to remove it entirely.

[panta82]

I "fixed" this locally via patch-package.