<h2 class="heading-medium">
  Optional content
</h2>
<p>
  Use double brackets and ‘??’ to define optional content.
</p>
<p>
  For example if you only want to show something to people who are under
  18:
</p>
<div class="panel panel-border-wide">
  <p>
    ((under18??Please get your application signed by a parent or
    guardian.))
  </p>
</div>
<p>
  For each person you send this message to, specify ‘yes’ or ‘no’ to
  show or hide this content.
</p>
