Added CLA assistant

README.md

@@ -1,3 +1,4 @@
+[![CLA assistant](https://cla-assistant.io/readme/badge/jrouwe/JoltPhysics)](https://cla-assistant.io/jrouwe/JoltPhysics)
 [![Build Status](https://github.com/jrouwe/JoltPhysics/actions/workflows/build.yml/badge.svg)](https://github.com/jrouwe/JoltPhysics/actions/)
 
 # Jolt Physics Library