Add support for Location Push Extension

[aaronpk]

https://developer.apple.com/documentation/corelocation/creating_a_location_push_service_extension?language=objc

This would let you force an update of the phone's location by sending a special push notification. You could use this to query the phone's location every hour even if the main tracking in the app is off.

The major implication of this is that only the app developer (me) will be able to send these push notifications since it requires apple developer credentials. So I would have to run a service for individual users to be able to query their own locations, which opens up a giant can of worms around running a server, accounts, storing data, etc.

This is likely a good candidate for a feature enabled with a paid subscription.