Update README.md

Author: qba73

README.md

@@ -7,6 +7,8 @@
 ![GitHub License](https://img.shields.io/github/license/qba73/pkgproxy)
 [![Scorecard](https://github.com/qba73/pkgproxy/actions/workflows/scorecard.yml/badge.svg)](https://github.com/qba73/pkgproxy/actions/workflows/scorecard.yml)
 [![OpenSSF Best Practices](https://www.bestpractices.dev/projects/10848/badge)](https://www.bestpractices.dev/projects/10848)
+![Maintenance](https://img.shields.io/badge/maintenance-actively--developed-brightgreen.svg)
+