Auto discovery deactivation at runtime by MQTT command (#856)

and switch automatic creation for it in HASS (by autodiscovery :-)

docs/use/gateway.md

@@ -15,6 +15,20 @@ With Home Assistant, this command is directly avalaible through MQTT auto discov
 With Home Assistant, this command is directly avalaible through MQTT auto discovery as a switch into the HASS OpenMQTTGateway device entities list.
 :::
 
+## Auto discovery
+You can deactivate the MQTT auto discovery function, this function enable to create automaticaly devices/entities with Home Assistant convention.
+### Deactivate
+`mosquitto_pub -t "home/OpenMQTTGateway/commands/MQTTtoSYS/config" -m '{"discovery":false}'`
+
+### Activate
+`mosquitto_pub -t "home/OpenMQTTGateway/commands/MQTTtoSYS/config" -m '{"discovery":true}'`
+
+If you want the settings to be kept upon gateway restart, you can publish the command with the retain flag.
+
+::: tip
+Auto discovery is enable by default on release binaries, on platformio (except for UNO). With Arduino IDE please read the [advanced configuration section](../upload/advanced-configuration#auto-discovery) of the documentation.
+:::
+
 # State LED usage
 
 The gateway can support up to 3 LED to display its operating state: