add opengraph descriptions

_includes/head.html

@@ -14,18 +14,31 @@
             content="{{ page.date | date_to_xmlschema }}"/>
         <meta property="article:section"
             content="Blog"/>
+
         {% for tag in page.tags %}
             <meta property="article:tag" content="{{ tag }}"/>
         {% endfor %}
+
         {% if page.image %}
             <meta property="og:image" 
                 content="{{site.url}}/images/{{page.path | split: '/' | last | split: '.' | first }}/{{page.image}}"/>
         {% endif %}
+
+        {% if page.description %}
+            <meta 
+                property="og:description"
+                content="{{page.description}}"
+            />
+        {% else %}
+            <meta 
+                property="og:description"
+                content="{{page.content | markdownify | strip_html | truncate: 100}}"
+            />
+        {% endif %}
     {% else %}
         <meta property="og:type" 
             content="website"/>
     {% endif %}
-    <!--{{page.collection}}-->
 
     <link rel="stylesheet" href="/fa/css/fontawesome.min.css">
     <link rel="stylesheet" href="/fa/css/brands.min.css">