[calendar][agenda] Feature request: calendar view of Gadgetbridge-synchronized events

`calendar` is a great app, having a nice calendar view and a nice agenda view. But it only shows events that have been explicitly added to the app; it does not show any events from my regular calendar on my phone (it appears to read from ~~"calendar.json"~~ "calendar.days.json").

`agenda` is a great app, having a nice agenda view of events synchronized from my phone via Gadgetbridge (it appears to read from "android.calendar.json"), and a detail view for each event. But it can't show those events in or alongside a calendar view.

I'm using both apps, but I find myself switching back and forth between them to make sense of when things are happening. It would be nice to have one app that can show synchronized events in a calendar view. I see three possible approaches for this:
1. Enhance `calendar` to also read events from the synchronized calendar.
2. Enhance `agenda` to add a calendar view.
3. Create a new app that does all of this.

For reference, I have a Bangle 2 on firmware 2v25, with `calendar` 0.18 and `agenda` 0.15. I also gave a quick try to `rebbleagenda` 0.02 and `calclock` 0.09, but like `agenda`, those do not have calendar views.