Add Contributor Covenant badge to README

Author: parkerbxyz

README.md

@@ -1,5 +1,7 @@
 # GitHub Training Manual: GitHub for Developers
 
+[![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](code_of_conduct.md)
+
 Welcome to the GitHub Training Manual repo. In this repo, you will find the content used by GitHub trainers during our official training courses and scripts used when teaching.
 
 ## Deploy the manual