Add classes from link title

source/_partials/navbar.html.twig

@@ -13,7 +13,7 @@
     <div id="navbar" class="collapse navbar-collapse">
       <ul class="nav navbar-nav">
         {% for link in site.main_menu %}
-          <li class="{{ link.class }}"><a href="{{ link.href }}">{{ link.title }}</a></li>
+          <li class="nav__{{ link.title | lower }}"><a href="{{ link.href }}">{{ link.title }}</a></li>
         {% endfor %}
       </ul>
     </div>{# .nav-collapse #}