optional context not typed

This is great for providing typed events, however, there doesn't seem to be any allowance for the optional context that can be passed to an event.

`PlayBus.on('botDestroyed', this.attemptSpawn, this)`

The above code is correct and passes the context correctly to eventemitter3, but typescript complains about the 'this'. Is this a mistake?
Should for example:

` on (event: E, listener: Events[E]): this`

instead be:

` on (event: E, listener: Events[E], context?: any): this`