Allow specifying deep sleep wakup clock time (#3312)

esphome/components/time/real_time_clock.h

@@ -88,6 +88,8 @@ struct ESPTime {
   /// Convert this ESPTime instance back to a tm struct.
   struct tm to_c_tm();
 
+  static int32_t timezone_offset();
+
   /// Increment this clock instance by one second.
   void increment_second();
   /// Increment this clock instance by one day.