uci-hugo-doc/layouts/shortcodes/expand.html

<div class="gdoc-expand">
  <label>
    <div class="gdoc-expand__head flex justify-between">
      <span>{{ default "Expand" (.Get 0) }}</span>
      <span>{{ default "↕" (.Get 1) }}</span>
    </div>
    <input type="checkbox" class="gdoc-expand__control hidden" />
    <div class="gdoc-markdown--nested gdoc-expand__content">
      {{ .Inner | markdownify }}
    </div>
  </label>
</div>