[Feature Request] Include msg-id's in Custom Widget API

I'm currently developing a custom chat widget and noticed that the onEventReceived listener doesn't seem to expose certain Twitch-specific tags. 
Specifically, the msg-id for announcements and viewermilestone appears to be missing from the event data. 
It would be a great improvement to have these IDs included, as it would allow us to style these special events natively within the overlay.