docs: add fragments class to training TOC

        </ul>

      </li>

      <li class="toggle-list">

        <div><a href="<?cs var:toroot ?>training/basics/fragments/index.html">

            <span class="en">Building a Dynamic UI with Fragments<span class="new">&nbsp;new!</span></span>

          </a></div>

        <ul>

          <li><a href="<?cs var:toroot ?>training/basics/fragments/support-lib.html">

            <span class="en">Using the Support Library</span>

          </a>

          </li>

          <li><a href="<?cs var:toroot ?>training/basics/fragments/creating.html">

            <span class="en">Creating a Fragment</span>

          </a>

          </li>

          <li><a href="<?cs var:toroot ?>training/basics/fragments/fragment-ui.html">

            <span class="en">Building a Flexible UI</span>

          </a>

          </li>

          <li><a href="<?cs var:toroot ?>training/basics/fragments/communicating.html">

            <span class="en">Communicating with Other Fragments</span>

          </a>

          </li>

        </ul>

      </li>

      <li class="toggle-list">

        <div><a href="<?cs var:toroot ?>training/basics/intents/index.html">

            <span class="en">Interacting with Other Apps<span class="new">&nbsp;new!</span></span>