Export webhook event types

[rosslavery]

Hi there,

Can you update the library to export the various webhook event types? This is useful for typing events for our incoming webhooks request controllers.

Example of unexported type:

type PhoneEvents = PhoneRecordingDeletedEvent | PhoneCallerCallLogCompletedEvent | .....

Would be great to have PhoneEvents and possibly the other individual events exported as well, like type PhoneRecordingDeletedEvent, etc.