Ecosystem Nav (vuejs#589)

* Update main_menu.ejs

* Update main_menu.ejs

* Create ecosystem_dropdown.ejs

* Update ecosystem_dropdown.ejs

Author: lukepolo

themes/vue/layout/partials/ecosystem_dropdown.ejs

@@ -0,0 +1,7 @@
+<li class="nav-dropdown-container">
+  <a class="nav-link">Ecosystem</a><span class="arrow"></span>
+  <ul class="nav-dropdown">
+    <li><a href="https://vuex.vuejs.org/en/" class="nav-link" target="_blank">Vuex</a></li>
+    <li><a href="https://router.vuejs.org/en/" class="nav-link" target="_blank">Vue Router</a></li>
+  </ul>
+</li>

themes/vue/layout/partials/main_menu.ejs

@@ -8,3 +8,4 @@
 <li><a href="/v2/examples/" class="nav-link<%- page.path.match(/examples/) ? ' current' : '' %>">Examples</a></li>
 <li><a href="https://medium.com/the-vue-point" target="_blank" class="nav-link<%- page.path.match(/blog/) ? ' current' : '' %>">Blog</a></li>
 <%- partial('partials/community_dropdown') %>
+<%- partial('partials/ecosystem_dropdown') %>