Immediately go to sleep if battery is critical (#274)

* Immediately go to sleep if battery is critical

* Turn off peripheral power in Battery critical shutdown just to be sure

src/Battery.cpp

@@ -29,8 +29,14 @@ void Battery_Init(void) {
 		Battery_LogStatus();
 
 		Log_Println(batteryCriticalMsg, LOGLEVEL_NOTICE);
+		// turn off peripheral power just to be sure, even if it should not yet have been turned on
+		Power_PeripheralOff();
 		// Power down and enter deepsleep
-		System_RequestSleep();
+		// Don't call System_RequestSleep() here: If the battery is critial, we want to avoid as much init work as possible
+		// and also any blinking lights or sounds. The goal is to just stay off.
+		// Additionally, LPCD will not be enabled. This is intentional to avoid battery drain.
+		delay(200);
+		esp_deep_sleep_start();
 	}
 	#endif
 }