Fix support for typed subscriptions for multiple event names for .on()

[arthur-er]

Closes #82

[sindresorhus]

Can you add it to all the methods that accept it? See: https://github.com/sindresorhus/emittery/pull/82/files

[arthur-er]

Can you add it to all the methods that accept it? See: https://github.com/sindresorhus/emittery/pull/82/files

I'm unsure about how to add the tests. But I added the type into the other methods

[sindresorhus]

They need to be tested for this to be merged.

[arthur-er]

They need to be tested for this to be merged.

Tests added!

[sindresorhus]

Tests are failing. Please always run npm test locally before pushing changes.

[arthur-er]

I'm getting issues with pEvent compatibility, the emitter in pEvent don't expect the emitter methods to receive an array