RTC - Realtime Clock

Duties 
 
 Emulate a DS1307 real time clock chip 
 Optionally implement extra ram set/recall 
 Optionally implement DS3231 alarms, temperature 
 
 Parts 
 
 Reuse the Teensy 4.1 that's handling Keyboard input 
 CR1220 Battery (recycled from 380XD repair)