Added Identifier to last element.

Added Identifier to last element. 
To fix processing/p5.js-website#615

Author: TheShubham99

src/templates/partials/sidebar.hbs

@@ -22,7 +22,7 @@ slug: sidebar
       <li><a href="{{root}}/showcase/">{{#i18n "Showcase"}}{{/i18n}}</a></li>
       <li><a href="https://discourse.processing.org/c/p5js" target=_blank class="other-link">{{#i18n "Forum"}}{{/i18n}}</a></li>
       <li><a href="http://github.com/processing/p5.js" target=_blank class="other-link">GitHub</a></li>
-      <li><a href="http://twitter.com/p5xjs" target=_blank class="other-link">Twitter</a></li>
+      <li><a href="http://twitter.com/p5xjs" target=_blank class="other-link" id="last">Twitter</a></li>
     </ul>
   </nav>
 </div>