Add link to table of orders to nav bar

InvenTree/part/templates/navbar.html

@@ -9,6 +9,7 @@
       <li><a href="/part/">Parts</a></li>
       <li><a href="/stock/">Stock</a></li>
       <li><a href="/supplier/">Suppliers</a></li>
+      <li><a href="/customer-orders/">Customer Orders</a></li>
     </ul>
   </div>
 </nav>