Add iot_class to hacs.json

This integration is Local Polling - advertise it.

hacs.json

@@ -10,5 +10,6 @@
     "NZ",
     "AU"
   ],
-  "homeassistant": "0.109.0"
+    "homeassistant": "0.109.0",
+  "iot_class": "Local Polling"
 }