title: featherlight loading msg before getting ajax data
body: <p>I have a typical link for which I would like to display the output in a popup window. To do that I'm using featherlight.
  I would like to display some kind of a loading indicator until I get data from ajax call.
  This is what I have tried:</p>
  
  <pre><code>    function wait() {
          document.querySelector('.featherlight-content').textContent='pls wait...';
      }
  
  &lt;a href='../servlet/NavWarn?action=send' data-featherlight="ajax" data-featherlight-before-content="wait();"&gt;
  </code></pre>
  
  <p>If I do that, it only prints "pls wait..." and the ajax data doesn't appear ever.
  If I remove the "data-featherlight-before-content" from the A tag, ajax data appears correctly, but until it does I get an empty window (which is what I would like to avoid).</p>
  
  <p>I've also tried doing it at featherlight's css (something like content:"pls wait...") without luck.</p>
  
  <p>Any ideas?
  Thank you</p>