go, a navigation menu
and an open button.
The navigation menu includes four parts, main navigation items,
sub navigation items, a search field and a close button.</p>

<p>The open button and the close button only shows on small screens
for toggling the navigation menu. Except these two buttons, all
the other parts in a navigation component can be optional.</p>

<p>A navigation component can be created with these classes:
<code class="highlighter-rouge">.nav-header</code>, <code class="highlighter-rouge">.na