docs/_includes/custom_builds.html

<div id="custom-builder">
  <div>
    <div id="custom-options">
    </div>
  </div>
  <div>
    <pre><code id="custom-code"></code></pre>
    <div id="custom-buttons">
      <div>
        <a id="download-custom" class="btn btn-primary" href="#">
          Download
        </a>
      </div>
      <div>
        <a id="download-custom-min" class="btn btn-primary" href="#">
          Download min
        </a>
      </div>
    </div>
  </div>
</div>

<script src="static/js/custom/builder.js"></script>