Add a slow display refresh mode to fast_stopwatch

watch-faces/complication/fast_stopwatch_face.h

@@ -59,6 +59,7 @@ typedef struct {
     rtc_counter_t lap_counter;   // rtc counter when the stopwatch was lapped
     rtc_counter_t stop_counter;  // rtc counter when the stopwatch was stopped
     uint8_t status;              // the status the stopwatch is in (idle, running, stopped)
+    bool slow_refresh;           // update the display slowly (same 128Hz timekeeping accuracy)
     struct {
         rtc_counter_t seconds;
         rtc_counter_t minutes;