Update README.md

Author: ChrisRackauckas

README.md

@@ -4,6 +4,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/SciML/ModelingToolkit.jl/badge.svg?branch=master)](https://coveralls.io/github/SciML/ModelingToolkit.jl?branch=master)
 [![Stable](https://img.shields.io/badge/docs-stable-blue.svg)](http://mtk.sciml.ai/stable/)
 [![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](http://mtk.sciml.ai/dev/)
+[![ColPrac: Contributor's Guide on Collaborative Practices for Community Packages](https://img.shields.io/badge/ColPrac-Contributor's%20Guide-blueviolet)](https://github.com/SciML/ColPrac)
 
 ModelingToolkit.jl is a modeling framework for high-performance symbolic-numeric computation
 in scientific computing  and scientific machine learning.