add device_class_signal_strength (#3058)

src/common/entity/sensor_icon.ts

@@ -9,6 +9,7 @@ const fixedDeviceClassIcons = {
   temperature: "hass:thermometer",
   pressure: "hass:gauge",
   power: "hass:flash",
+  signal_strength: "hass:wifi",
 };
 
 export default function sensorIcon(state: HassEntity) {

src/util/hass-attributes-util.js

@@ -34,6 +34,7 @@ hassAttributeUtil.DOMAIN_DEVICE_CLASS = {
     "temperature",
     "pressure",
     "power",
+    "signal_strength",
   ],
 };