app/index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Manta</title>
    <link rel="stylesheet" href="../static/css/bootstrap.min.css"></link>
    <link rel="stylesheet" href="../static/css/ionicons.min.css"></link>
    <link rel="stylesheet" href="../static/css/general.css"></link>
    <link rel="stylesheet" href="../static/css/layout.css"></link>
    <link rel="stylesheet" href="../static/css/form.css"></link>
    <link rel="stylesheet" href="../static/css/contact.css"></link>
    <link rel="stylesheet" href="../static/css/items.css"></link>
    <link rel="stylesheet" href="../static/css/date-picker.css"></link>
  </head>
  <body>
    <div id="root"></div>
    <script>
      {
        const scripts = [];
        const isDev = require('electron-is-dev');
        if (isDev) {
          scripts.push(
            'http://localhost:3000/main.dev.js'
          );
        } else {
          scripts.push(
            '../prod/main.prod.js'
          );
        }
        document.write(
          scripts
            .map(script => '<script defer src="' + script + '"><\/script>')
            .join('')
        );
      }
    </script>
  </body>
</html>