_settings_loop() never handled EVENT_TIMEOUT, so leaving the watch
face parked in settings mode (4Hz tick, blinking abbreviation) with
no button presses meant it stayed there indefinitely instead of
returning to the clock display like every other face's settings mode
does on timeout.
Factor the existing EVENT_MODE_BUTTON_UP transition logic into
_exit_settings_mode() and reuse it for EVENT_TIMEOUT.
Improvements:
- The name of the time zone is displayed for a brief movement when cycling through the selected time zones.
- The face now comes with pre-selected zones to show-case its functionality: Seattle, New York, UTC, Shanghai, and Tokyo.
Konrad Rieck