docs: Add rad clone badge in README

Author: pawamoy

README.md

@@ -4,6 +4,7 @@
 [![documentation](https://img.shields.io/badge/docs-mkdocs-708FCC.svg?style=flat)](https://mkdocstrings.github.io/griffe/)
 [![pypi version](https://img.shields.io/pypi/v/griffe.svg)](https://pypi.org/project/griffe/)
 [![gitter](https://img.shields.io/badge/matrix-chat-4db798.svg?style=flat)](https://app.gitter.im/#/room/#mkdocstrings_griffe:gitter.im)
+[![radicle](https://img.shields.io/badge/rad-clone-6666FF.svg?style=flat)](https://app.radicle.at/nodes/seed.radicle.at/rad:z4M5XTPDD4Wh1sm8iPCenF85J3z8Z)
 
 <img src="https://raw.githubusercontent.com/mkdocstrings/griffe/main/logo.svg" alt="Griffe logo, created by François Rozet" width="200" align="right">