README: Add PyPI badge

Author: noelleleigh

README.md

@@ -2,10 +2,13 @@
 
 Federation support for ![Graphene Logo](http://graphene-python.org/favicon.png) [Graphene](http://graphene-python.org) following the [Federation specifications](https://www.apollographql.com/docs/apollo-server/federation/federation-spec/).
 
+[![PyPI version][pypi-image]][pypi-url]
 [![Unit Tests Status][unit-tests-image]][unit-tests-url]
 [![Coverage Status][coveralls-image]][coveralls-url]
 [![Integration Tests Status][integration-tests-image]][integration-tests-url]
 
+[pypi-image]: https://badge.fury.io/py/graphene-federation.svg
+[pypi-url]: https://pypi.org/project/graphene-federation/
 [unit-tests-image]: https://github.com/graphql-python/graphene-federation/workflows/Unit%20Tests/badge.svg?branch=main
 [unit-tests-url]: https://github.com/graphql-python/graphene-federation/actions?query=workflow%3A"Unit+Tests"
 [coveralls-image]: https://coveralls.io/repos/github/graphql-python/graphene-federation/badge.svg?branch=main