Add an iot_class back into the manifest.

Last week hassfest was complaining when it was there. This week it is complaining when it is not.

custom_components/tuya_local/manifest.json

@@ -1,5 +1,6 @@
 {
     "domain": "tuya_local",
+    "iot_class": "local_polling",
     "name": "Tuya based devices local control",
     "version": "0.2.1", 
     "documentation": "https://github.com/make-all/tuya-local",