index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'">
    <link href="./styles.css" rel="stylesheet">
    <title>Website Previewer</title>
  </head>
  <body>
    
    <div class="content">

      <h2>Website Previewer</h2>
      
     https://<input type="text" value="github.com" id="url">
     <input type="submit" id="submit" value="Preview">

     <br>
     <small>powered by Electron <span id="electron-version"></span> | Sourcecode on <a href="https://github.com/Mario-Greiner/WebsitePreviewer" target="_blank">GitHub</a></small>
    </div>
    
    <!-- You can also require other files to run in this process -->
    <script src="./renderer.js"></script>
  </body>

</html>