Add PDF version of TRs and create resources section

Author: melissawm

docs/source/_static/images/JAX_ecosystem.svg

@@ -7,7 +7,7 @@
             <ul class="dropdown-menu">
                 <li><a class="dropdown-item" href="getting_started.html">Get Started</a></li>
                 <li><a class="dropdown-item" href="tutorials.html">Tutorials</a></li>
-                <li><a class="dropdown-item" href="ecosystem_overview/the_ecosystem_overview_tr.html">Learn more about the JAX AI Ecosystem</a></li>
+                <li><a class="dropdown-item" href="learn_ecosystem.html">Learn more about the JAX AI Ecosystem</a></li>
             </ul>
         </li>
         <li class="nav-item dropdown">