Add PyPI badge to README.md

Author: cottsay

README.md

@@ -3,6 +3,7 @@ createrepo-agent
 
 [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/osrf/createrepo-agent/ci.yaml?branch=main&event=push)](https://github.com/osrf/createrepo-agent/actions/workflows/ci.yaml?query=branch%3Amain+event%3Apush)
 [![Codecov branch](https://img.shields.io/codecov/c/gh/osrf/createrepo-agent/main)](https://app.codecov.io/gh/osrf/createrepo-agent/tree/main)
+[![PyPI package](https://img.shields.io/pypi/v/createrepo-agent)](https://pypi.org/project/createrepo-agent)
 
 *Rapidly and repeatedly generate RPM repository metadata*