title: Close all open Featherlight windows before opening a new one
body: <p>I'm registering multiple featherlight instances upon page-load</p>
  
  <pre><code>jQuery('.feedback').featherlight(jQuery( "#feedback-box" ), { closeIcon: 'close'});
  jQuery('#imprint').featherlight(jQuery( "#imprint-box" ), { closeIcon: 'close'});
  </code></pre>
  
  <p>When one box is opened I would like to close all other open ones before.</p>
  
  <p>How can I achieve this?</p>
  
  <p><strong>Edit:</strong> I tried this but it doesn't work.</p>
  
  <pre><code>$('.feedback').featherlight($( "#feedback-box" ), { 
      closeIcon: 'close', 
      beforeOpen: $.featherlight.close()
  });
  </code></pre>