[HM-RD] Added leak/water detection sensor with ESP32 deep sleep / sensor wake (#1615)

Added leak/water detection sensor with ESP32 deep sleep / sensor wake

docs/use/boards.md

@@ -92,19 +92,22 @@ OpenMQTTGateway support a low power mode for ESP32, this mode can be set by MQTT
 The low power mode can be changed also with a push to button B when the board is processing (top button on M5stickC, M5stickC Plus and middle button of M5stack).
 If you are already in low power mode 1 or 2 with M5Stack you can wake up the board by pressing the red button.
 
-### Low power mode (deepSleep) for ESP8266 boards
-In certain use cases where power is severly limited you can use the ESP8266 deep sleep capability.
+### Low power mode (deepSleep) for ESP8266 & ESP32 boards
+In certain use cases where power is severly limited you can use the ESP8266 or ESP32 deep sleep capability.
 
 * e.g. measuring a pool temperature every 5 minutes using an ESP8266 and DS18B20 probe where the ESP8266 is powered by very limited battery backed solar power.
+* e.g. as a water/leak detector which wake-up based on sensor state an ESP32 and C-37 YL-83 HM-RD sensor where the ESP32 is powered by very limited battery power.
 
 During deep sleep everything is off and (almost) all execution state is lost. 
 
-Consumption is about 20 µA.
+Consumption is about 20 µA on an ESP8266.
 
-Use this when you want the device to sleep for minutes or hours.
+Use this when you want the device to sleep for minutes,  hours woken by external sensor state.
 
-You only have to define the macro `ESP8266_DEEP_SLEEP_IN_US` with the number of microseconds.
+You only have to define the macro `DEEP_SLEEP_IN_US` with the number of microseconds, this works for both ESP8266 and ESP32.
 
-A hardware jumper is required connecting RST to a GPIO (not to CH_PD) defined by the macro `ESP8266_DEEP_SLEEP_WAKE_PIN` and defaulted to D0.
+For an ESP8266 a hardware jumper is required connecting RST to a GPIO (not to CH_PD) defined by the macro `ESP8266_DEEP_SLEEP_WAKE_PIN` and defaulted to D0.
+
+On an ESP32 we can also use an external sensor state to wake-up the ESP and this is defined by macro `ESP32_EXT0_WAKE_PIN` and which state it must toggle to by macro `ESP32_EXT0_WAKE_PIN_STATE` defaulted to 1 (high).
 
 And the sensor code must set variable `ready_to_sleep` to true after publishing the measurement to MQTT and the main loop will then enter deep sleep.