add ocpp versions supported

Author: drc38

README.md

@@ -5,7 +5,7 @@
 
 ![OCPP](https://github.com/home-assistant/brands/raw/master/custom_integrations/ocpp/icon.png)
 
-This is a Home Assistant integration for Electric Vehicle chargers that support the Open Charge Point Protocol.
+This is a Home Assistant integration for Electric Vehicle chargers that support the following Open Charge Point Protocols 1.6j, 2.0.1 and 2.1 (experimental).
 
 * based on the [Python OCPP Package](https://github.com/mobilityhouse/ocpp).
 * HACS compliant repository