Adds a11y landmarks

_layouts/default.html

@@ -20,7 +20,7 @@
     {% include sidebar.html %}
 
     <div class="content__overlay"></div>
-    <div class="content__area">
+    <main class="content__area" role="main">
       <div class="content">
         <button class="menu-button">
           <i class="icon fa fa-2x fa-bars" aria-hidden="true"></i>
@@ -29,7 +29,7 @@
         <h1>{{ page.title }}</h1>
         {{ content }}
       </div>
-    </div>
+    </main>
   </body>
   <script src="{{ '/js/script.js' | prepend: site.baseurl }}"></script>
 </html>