message: update react-scripts readme
  warn about changes in CRA and version lock
diff: @@ -20,5 +20,7 @@ $ yarn
  $ yarn start
  ```
  +> Note: due to recent changes with how create-react-app handles external customization, we are forced to lock our react-scripts package to an older version of create-react-app (v3.2.0).
  +
  ## License
  Copyright (c) 2017 Wix.com Ltd. All Rights Reserved. Use of this source code is governed by an [MIT license](./LICENSE).
  