Fix link to contribution guidelines in README (#1855)

Author: fleaz

README.md

@@ -70,7 +70,7 @@ This is an active open-source project. We are always open to people who want to
 use the code or contribute to it.
 
 We've set up a separate document for our
-[contribution guidelines](CONTRIBUTING.md).
+[contribution guidelines](.github/CONTRIBUTING.md).
 
 Thank you for being involved! :heart_eyes: