docs: add additional stories

• docs: add story for jumbotron
• docs: add dropdown navbar
• docs: add story for direct nav
• docs: add story for promotion widget
• docs: add story for working group list widget

stories/layout/jumbotron.stories.ts

@@ -87,6 +87,13 @@ export const Default: Story = {
                   `
                   : ''
                 }
+                <ul class="list-inline">
+                  <li>
+                    <a class="btn btn-primary" href="#">
+                      Text
+                    </a>
+                  </li>
+                </ul>
               </div>
             </div>
           </div>