Add linkedin meta tag

Author: vgvassilev

Diff for: _includes/head.html

@@ -4,6 +4,9 @@
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>{% if page.title %}{{ page.title | escape }}{% else %}{{ site.title | escape }}{% endif %}</title>
   <meta name="description" content="{% if page.excerpt %}{{ page.excerpt | strip_html | strip_newlines | truncate: 160 }}{% else %}{{ site.description }}{% endif %}">
+  {% if page.banner_image %}
+  <meta name="og:image" content="{{ site.url }}{{ site.baseurl }}/{{page.banner_image}}">
+  {% endif %}
   <link rel="stylesheet" href="{{ "/css/main.css" | prepend: site.baseurl | prepend: site.url}}">
   <link rel="stylesheet" href="{{ "/css/syntax.css" | prepend: site.baseurl | prepend: site.url}}">
   <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}">