add method for removing custom event listeners

[Mohmn]

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[dadiorchen]

Yes, this is good, now we are using node built-in (if I can say this way) event API to handle the event listener, so it seems easy to expose something @Mohmn required in this issue.

https://nodejs.org/api/events.html

[Mohmn]

@dadiorchen yep its pretty straight forward, should i do it myself or leave it for the new contributors

[dadiorchen]

I hope you can take it, it is not a easy one

[Mohmn]

I hope you can take it, it is not a easy one

I will give it a go then