added note about different cli versions

Author: emin93

CONTRIBUTING.md

@@ -4,6 +4,8 @@ Contributing to this project should be as easy and transparent as possible.
 
 ## Workflow
 
+Right now there are two master branches in order to keep support for the old React Native CLI (for more info, check out the [related issue](https://github.com/react-native-community/react-native-template-typescript/issues/39)).
+
 We use [GitHub Flow](https://guides.github.com/introduction/flow/), so all code changes happen through pull requests.
 
 1.  Fork the repository and create your branch from `master`.