Initialize Froala WYSIWYG editor with font size plugin

HTML

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <script src="https://cdn.jsdelivr.net/npm/froala-editor@5.2.0/js/froala_editor.min.js"></script>
  <script src="https://cdn.jsdelivr.net/npm/froala-editor@5.2.0/js/plugins/font_size.min.js"></script>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/froala-editor@5.2.0/css/froala_style.min.css">
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/froala-editor@5.2.0/css/froala_editor.pkgd.min.css">
</head>
<body>
  <textarea id="froala-editor">&lt;p&gt;abc&lt;/p&gt;</textarea>
  <script>
    new FroalaEditor('#froala-editor', {
      key: '',
      fontSizeDefaultSelection: '20'
    });
  </script>
</body>
</html>