Write app glance in wakeup_schedule_simple_robust to ensure time is accurate

src/c/scheduler.h

@@ -0,0 +1,4 @@
+#pragma once
+#include <pebble.h>
+
+WakeupId wakeup_schedule_simple_robust(time_t wakeup_time, int8_t retry_diff, bool is_fallback);