create events in calendar when new readings, to support Apple Watch

Option to write latest glucose value in Calendar event. This allows to make reading visible in Apple Watch.

Following instructions are copied from Spike :
On your Apple Watch or the Watch app in your iOS device select the
"Modular" watch face and make sure you also select the "Calendar Complication" to be present in the middle of the watch face
Your glucose values should now start syncing to your watch when you receive your next reading from your CGM transmitter.
If by any chance you're not getting readings in your Apple Watch, go to the Watch app and under "General", "Reset"
click the "Reset Sync Data" and wait a few minutes.