add docs for setting up CircleCI for CRA (facebook#2423)

* add docs for setting up CircleCI for CRA

* Reword

Author: knowbody

packages/react-scripts/template/README.md

@@ -1259,6 +1259,10 @@ script:
 1. Trigger your first build with a git push.
 1. [Customize your Travis CI Build](https://docs.travis-ci.com/user/customizing-the-build/) if needed.
 
+#### CircleCI
+
+Follow [this article](https://medium.com/@knowbody/circleci-and-zeits-now-sh-c9b7eebcd3c1) to set up CircleCI with a Create React App project.
+
 ### On your own environment
 ##### Windows (cmd.exe)