feat(emitter): add listenIf method

[RomainLanz]

Hey there! 👋🏻

This PR adds the listenIf method. This method allows listening to an event only if the condition returns true.

Instead of...

if (app.inDev) {
  emitter.on(...)
}

You can write:

emitter.listenIf(app.inDev, () => {})

It seems that TypeScript is not happy about the overloading when calling this.on(), I am not sure how to fix that.

[thetutlage]

Yeah, one of those weirdo issues where TypeScript is struggling to match the correct overload. For you we can say this.on(event as any, listener)

[RomainLanz]

Yup, I went with a @ts-expect-error. If TypeScript "fixes" this one day, we will have a warning and be able to remove the comments.

It is more elegant than casting event to any.

[thetutlage]

Agree!