Add unit_of_measurment to linkquality sensor. https://github.com/Koenkk/zigbee2mqtt/issues/883

lib/extension/homeassistant.js

@@ -170,6 +170,7 @@ const configurations = {
         type: 'sensor',
         object_id: 'linkquality',
         discovery_payload: {
+            unit_of_measurement: 'RSSI',
             value_template: '{{ value_json.linkquality }}',
         },
     },