Add types for event emitters

[moltar]

In this kind of code, the job is not properly typed.

worker.on('completed', job => {
  console.log(job)
})

Would be ideal, if this had at least the Job type, but ideally propagate the type all the way from the worker generic to the job.

May also find the following modules interesting:

• https://github.com/garronej/ts-evt
• https://github.com/rogierschouten/ts-events

[manast]

yes, this is a know limitation. Not so trivial to do in practice at least I did not find a really good way to solve it.

[manast]

btw, won't add a new dependency only for events, but thanks for the reference to the modules, they can be used for inspiration.

[roggervalf]

@moltar please try last version, event listener typing was added