improve accessibility and add search form

_layouts/post.html

@@ -8,7 +8,7 @@ layout: default
   {% include back-link.html %}
 {% endif %}
 
-<article class="post h-entry" itemscope itemtype="http://schema.org/BlogPosting" id="main">
+<article class="post h-entry" itemscope itemtype="http://schema.org/BlogPosting" id="main" role="article" aria-label="Content">
 
   {% if page.title != "" %}
     <h1 class="post-title divided p-name" itemprop="name headline">