Update example code (#12315)

path and url needed to be require'd

docs/tutorial/first-app.md

@@ -106,6 +106,8 @@ for the application to be ready and open a window:
 
 ```javascript
 const {app, BrowserWindow} = require('electron')
+const path = require('path')
+const url = require('url')
 
 function createWindow () {
   // Create the browser window.