Update README.md (#288)

Author: jbampton

README.md

@@ -3,6 +3,7 @@
 [![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](LICENSE)
 [![Built with Eleventy](https://img.shields.io/badge/Built%20with-Eleventy-black)](https://www.11ty.dev/)
 [![Run JavaScript Everywhere](https://img.shields.io/badge/Run%20JavaScript%20Everywhere-yellow)](https://nodejs.org/en)
+[![Built with Nunjucks](https://img.shields.io/badge/Built%20with-Nunjucks-darkgreen)](https://mozilla.github.io/nunjucks/)
 [![Built with Tailwind CSS](https://img.shields.io/badge/Built%20with-Tailwind-blue)](https://tailwindcss.com/)
 
 > A vibrant community directory showcasing open-source developers and software engineers from around the world.