Add Create React App video

Author: AryanJ-NYC

src/pages/installation/create-react-app.mdx

@@ -34,12 +34,20 @@ yarn create react-app your-app-name --typescript
 
 ## Add TypeScript to an Existing Create React App Application
 
+### Using NPM
+
 ```
 npm install --save typescript @types/node @types/react @types/react-dom @types/jest
 ```
 
+or
+
+### Using Yarn
+
 ```
 yarn add typescript @types/node @types/react @types/react-dom @types/jest
 ```
 
 After installing these (and any other [types](http://definitelytyped.org/) you may need), rename your `.js` files to `.tsx` and restart your development server.
+
+[This video](https://www.youtube.com/watch?v=wvvNUr4lgaM) runs through the instructions on this page.