title: Detect if a page is loading any resources
body: <p>Is it possible to determine if a page is loading any resources, at any time including after the HTML document loads or from new ajax requests?</p>
  
  <p>The use case is I have a site where I need to take a screenshot, but want to wait until everything has rendered. So this means:</p>
  
  <ol>
  <li>DOM has fully loaded (detecting this is easy even with plain JS)</li>
  <li>All resources (css, js, etc) have loaded.</li>
  <li>Any AJAX calls that may have occurred from actions have completed. (probably the hard part here)</li>
  </ol>
  
  <p>Detecting animations and CSS transitions is difficult, and not necessary for this. If you have a solution that covers 1-3, I will accept it. If you also know how to detect CSS transitions and JS animations etc, then you're amazing and I'll accept that :)</p>