Add support for discovery device trigger (#1090)

* Add announce of DeviceTrigger +  Update doc

main/config_RF.h

@@ -82,7 +82,7 @@ int minimumRssi = 0;
 #define RF_EMITTER_REPEAT  20
 #define RF2_EMITTER_REPEAT 2 // Actual repeats is 2^R, where R is the here configured amount
 //#define RF_DISABLE_TRANSMIT //Uncomment this line to disable RF transmissions. (RF Receive will work as normal.)
-//#define RFmqttDiscovery true //uncomment this line so as to create a discovery switch for each RF signal received
+#define RFmqttDiscovery true //uncomment this line so as to create a discovery switch for each RF signal received
 
 /*-------------------RF2 topics & parameters----------------------*/
 //433Mhz newremoteswitch MQTT Subjects and keys