Fix CRA code splitting link (#1765)

Author: RaedsLab

content/docs/code-splitting.md

@@ -102,7 +102,7 @@ import("./math").then(math => {
 
 When Webpack comes across this syntax, it automatically starts code-splitting
 your app. If you're using Create React App, this is already configured for you
-and you can [start using it](https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#code-splitting) immediately. It's also supported
+and you can [start using it](https://facebook.github.io/create-react-app/docs/code-splitting) immediately. It's also supported
 out of the box in [Next.js](https://github.com/zeit/next.js/#dynamic-import).
 
 If you're setting up Webpack yourself, you'll probably want to read Webpack's