add config details

config/custom_components/example.py

@@ -8,6 +8,22 @@ Example component to target an entity_id to:
  - turn it off if all lights are turned off
  - turn it off if all people leave the house
  - offer a service to turn it on for 10 seconds
+
+Configuration:
+
+To use the Example custom component you will need to add the following to
+your config/configuration.yaml
+
+example:
+  target: TARGET_ENTITY
+
+Variable:
+
+target
+*Required
+TARGET_ENTITY should be one of your devices that can be turned on and off,
+ie a light or a switch. Example value could be light.Ceiling or switch.AC
+(if you have these devices with those names).
 """
 import time
 import logging