feat(ios): resource update UI, information

**Is your feature request related to a problem? Please describe.**
This is a bit related to #199 and will likely be most easily addressed around the same time.

Currently, whenever the app notifies users that updates for their keyboards and/or lexical models are available, we present them, along with minimum feedback, with this fellow (the 'green' bit below):

The initial notification simply says "Updates Available"; the one seen above is, sadly, the most informative part of the process. The app (currently) says nothing of _which_ resources need updating, etc. Just that _something_ needs updating.

Be sure to refer to #3372; its changes were explicitly designed with enhancements like this in mind.

**Describe the solution you'd like**

... the UI aspects of this will certainly need some design work. We'll at least want _something_ that at least gives the names of the keyboards & lexical models to be updated. Possibly a popup-alert or something?

Extra design work will likely be needed for joint consideration with #199, especially if we make moves to support a background-notification style of update. Triggering an update from outside of the app will likely have extra constraints to be considered, though there's a good chance such "triggers" could link back into the app for whatever our preferred update-UI might be.