aligns file name with import to avoid build failure

Author: baywet

tutorial/02-create-app.md

@@ -34,7 +34,7 @@ npm install [email protected] [email protected] @microsoft/[email protected]
 
 ## Design the app
 
-Start by creating a navbar for the app. Create a new file in the `./src` directory named `Navbar.js` and add the following code.
+Start by creating a navbar for the app. Create a new file in the `./src` directory named `NavBar.js` and add the following code.
 
 ```JSX
 import React from 'react';