Added Python compatibility badge

Author: sergioteula

README.md

@@ -3,6 +3,7 @@ Amazon Product Advertising API 5.0 wrapper for Python
 A simple Python wrapper for the last version of the Amazon Product Advertising API.
 
 [![PyPI](https://img.shields.io/pypi/v/python-amazon-paapi5?color=%231182C2&label=PyPI)](https://pypi.org/project/python-amazon-paapi5/)
+[![Python](https://img.shields.io/badge/Python-2.x%20%7C%203.x-%23FFD140)](https://www.python.org/)
 [![License](https://img.shields.io/badge/License-GPL--3.0-%23e83633)](https://github.com/sergioteula/python-amazon-paapi5/blob/master/LICENSE)
 [![Support](https://img.shields.io/badge/Support-Good-brightgreen)](https://github.com/sergioteula/python-amazon-paapi5/issues)
 [![Amazon API](https://img.shields.io/badge/Amazon%20API-5.0-%23FD9B15)](https://webservices.amazon.com/paapi5/documentation/)