:bug: Support strict mode on Tutorial

[ci skip]

docs/tutorial/quick-start.md

@@ -78,6 +78,8 @@ The `main.js` should create windows and handle system events, a typical
 example being:
 
 ```javascript
+'use strict';
+
 const electron = require('electron');
 const app = electron.app;  // Module to control application life.
 const BrowserWindow = electron.BrowserWindow;  // Module to create native browser window.