Update sensor.mqtt.markdown (home-assistant#4968)

molobrakos · fabaff · commit 77c282d62f1e · 2018-03-23T11:31:35.000+01:00
diff --git a/source/_components/sensor.mqtt.markdown b/source/_components/sensor.mqtt.markdown
@@ -44,6 +44,10 @@ unit_of_measurement:
   description: Defines the units of measurement of the sensor, if any.
   required: false
   type: string
+icon:
+  description: Icon for the sensor (e.g. `mdi:gauge`).
+  required: false
+  type: string
 expire_after:
   description: Defines the number of seconds after the value expires if it's not updated.
   required: false
