Add badge for publication on Moodle.org

Author: x-name15

README.md

@@ -3,6 +3,7 @@
 [![Moodle](https://img.shields.io/badge/Moodle-4.1%2B-orange)](https://moodle.org)
 [![PHP](https://img.shields.io/badge/PHP-8.0%2B-blue)](https://php.net)
 [![License](https://img.shields.io/badge/License-GPL%20v3-green)](LICENSE)
+![Published on Moodle.org](https://img.shields.io/badge/Published%20on-Moodle.org-green)
 
  # **Officially published on Moodle.org:** [local_mrca](https://moodle.org/plugins/local_mrca) 🎉