Update README.md

Author: Mbd06b

README.md

@@ -1,4 +1,4 @@
-[![Contribute](https://www.eclipse.org/che/contribute.svg)](https://code.ethosengine.com/#https://github.com/ethosengine/che-starter?che-editor=che-incubator/che-idea/next)
+[![Contribute](https://www.eclipse.org/che/contribute.svg)](https://code.ethosengine.com/#{{GITHUB_REPO_URL}}?che-editor=che-incubator/che-idea/next)
 
 # che-starter
 A repository template starting an eclipse-che workspace with updates and tooling from ethosengine images.