title: How best to trigger event on file drop?
body: <p>Simple enough question, but I've spent a few hours and can't figure it out.</p>
  
  <p>Some background:</p>
  
  <ol>
  <li>Using dropzone.js I have set an entire page to be a dropzone.</li>
  <li>I properly handle the file upload.</li>
  </ol>
  
  <p>Issue:</p>
  
  <p>I want to trigger a JavaScript function to do something (lets say trigger an alert) whenever a person drops any file anywhere on the screen.  How would I best achieve this?</p>