Add separate file for running controller & update readme

app.py

@@ -0,0 +1,12 @@
+from controller import Controller
+
+Controller(
+  broker="mqtt.broker.ip",
+  port=8883,
+  mac="THINGY:52:MAC",
+  username="mqtt_username",
+  password="mqtt_password",
+  topic="homeassistant/sensor/thingy52",
+  caCertPath="/path/to/ca.crt",
+  temperatureOffset=-11
+)