fix(http2): send ping frames

[AndrewBarba]

Problem

#97

Solution

Reach into undici internals to send the ping frame. Not ideal, but fixes the immediate issues

[kohenkatz]

Thanks. I'm going to have to figure out how to test this without affecting our main application where I saw the problem.

I'm curious where you got pinging every 30 seconds - the documentation I saw said to ping once an hour: https://developer.apple.com/documentation/usernotifications/sending-notification-requests-to-apns#Follow-best-practices-while-sending-push-notifications-with-APNs

[AndrewBarba]

I just matched what I had in fetch-http2. If 30 is too aggressive I'll up it to 5-10min