Added open-graph extras

_includes/open-graph.html

@@ -16,4 +16,9 @@
 	<meta property="og:title" content="{% if page.title %}{{ page.title }}{% else %}{{ site.title }}{% endif %}">
 	{% if page.excerpt %}<meta property="og:description" content="{{ page.excerpt | strip_html }}">{% endif %}
 	<meta property="og:url" content="{{ page.url | replace:'index.html','' | prepend: site.url }}">
-	<meta property="og:site_name" content="{{ site.title }}">
+	<meta property="og:site_name" content="{{ site.title }}">
+	{% if page.image.feature %}
+	<meta name="og:image" content="{{ site.url }}/images/{{ page.image.feature }}">
+	{% else %}
+	<meta name="og:image" content="{% if page.image.thumb %}{{ site.url }}/images/{{ page.image.thumb }}{% else %}{{ site.url }}/images/{{ site.logo }}{% endif %}">
+	{% endif %}