Adding a code coverage badge

README.md

@@ -19,6 +19,7 @@ Official builds of this extension are available at [the official website](https:
 
 
 [![Build status](https://ci.appveyor.com/api/projects/status/dl8is5iqwt9qf3t7/branch/master?svg=true)](https://ci.appveyor.com/project/github-windows/visualstudio/branch/master)
+[![codecov](https://codecov.io/gh/GitHub/VisualStudio/branch/master/graph/badge.svg)](https://codecov.io/gh/GitHub/VisualStudio)
 
 [![Join the chat at freenode:github-vs](https://img.shields.io/badge/irc-freenode:%20%23github--vs-blue.svg)](http://webchat.freenode.net/?channels=%23github-vs) [![Join the chat at https://gitter.im/github/VisualStudio](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/github/VisualStudio?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)