* Put something on screen
* Use the 32bit watch_date_time repr to pass from JS
* Implement periodic callbacks
* Clear display on enabling
* Hook up watch_set_led_color() to SVG (green-only)
* Make debug output full-width
* Remove default Emscripten canvas
* Implement sleep and button clicks
* Fix time zone conversion bug in beats-time app
* Clean up warnings
* Fix pin levels
* Set time zone to browser value (if available)
* Add basic backup data saving
* Silence format specifier warnings in both targets
* Remove unnecessary, copied files
* Use RTC pointer to clear callbacks (if available)
* Use preprocessor define to avoid hardcoding MOVEMENT_NUM_FACES
* Change each face to const preprocessor definition
* Remove Intl.DateTimeFormat usage
* Update shell.html title, header
* Add touch start/end event handlers on SVG buttons
* Update shell.html
* Update folder structure (shared, simulator, hardware under watch-library)
* Tease out shared components from watch_slcd
* Clean up simulator watch_slcd.c inline JS calls
* Fix missing newlines at end of file
* Add simulator warnings (except format, unused-paremter)
* Implement remaining watch_rtc functions
* Fix button bug on mouse down then drag out
* Implement remaining watch_slcd functions
* Link keyboard events to buttons (for keys A, L, M)
* Rewrite event handling (mouse, touch, keyboard) in C
* Set explicit text UTF-8 charset in shell.html
* Address PR comments
* Remove unused directories from include paths
Vendor code from https://github.com/Netthaw/TOTP-MCU to do the
heavy lifting of computing SHA-1 and HMAC and the rest of TOTP
Also implement a date_time to unix timestamp method
