Add state_class to tomorrowio UV Index (#98541)

* Added state_class to UV Index

Forgot to add a state_class as other sensors got their state_class from their device class. As there is no UV Index device class I left it out.

* Forgotten a comma, whoops

* Changed measurement to string.

* Changed from "measurement" to SensorStateClass

homeassistant/components/tomorrowio/sensor.py

@@ -18,6 +18,7 @@ from homeassistant.components.sensor import (
     SensorDeviceClass,
     SensorEntity,
     SensorEntityDescription,
+    SensorStateClass,
 )
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import (
@@ -295,6 +296,7 @@ SENSOR_TYPES = (
     TomorrowioSensorEntityDescription(
         key=TMRW_ATTR_UV_INDEX,
         name="UV Index",
+        state_class=SensorStateClass.MEASUREMENT,
         icon="mdi:sun-wireless",
     ),
     TomorrowioSensorEntityDescription(