title: add class with scrolling bottom of page
body: <p>I have right/bottom fixed navigation like this.</p>
  
  <pre><code>&lt;div style='position:fixed; bottom:10px; right:10px;'&gt;NAVIGATION&lt;/div&gt;
  </code></pre>
  
  <p>when scrolling to the bottom of page, I want to add class (bottom:100px) to navigation.
  some help :-)</p>