add facebook meta

README.md

@@ -53,12 +53,16 @@ The SEO tag will respect any of the following if included in your site's `_confi
 * `description` - A short description (e.g., A blog dedicated to reviewing cat gifs)
 * `url` - The full URL to your site. Note: `site.github.url` will be used by default.
 * `twitter:username` - The site's Twitter handle. You'll want to describe it like so:
-
   ```yml
   twitter:
     username: benbalter
   ```
-
+* `facebook:app_id` (A Facebook app ID for Facebook insights), and/or `facebook:publisher` (A Facebook page URL or ID of the publishing entity). You'll want to describe one or both like so:
+   ```yml
+   facebook:
+     app_id: 1234
+     publisher: 1234
+   ```
 * `logo` - Relative URL to a site-wide logo (e.g., `assets/your-company-logo.png`)
 * `social` - For [specifying social profiles](https://developers.google.com/structured-data/customize/social-profiles). The following properties are available:
   * `type` - Either `person` or `organization` (defaults to `person`)

lib/template.html

@@ -79,12 +79,15 @@
 
 {% if page.date %}
   <meta property="og:type" content="article" />
+  <meta property="article:published_time" content="{{ page.date | date_to_xmlschema }}" />
+
   {% if page.next.url %}
     <link rel="next" href="{{ page.next.url | prepend: seo_url | replace:'/index.html','/' }}" title="{{ page.next.title | escape }}" />
   {% endif %}
   {% if page.previous.url %}
     <link rel="prev" href="{{ page.previous.url | prepend: seo_url | replace:'/index.html','/' }}" title="{{ page.previous.title | escape }}" />
   {% endif %}
+
   <script type="application/ld+json">
     {
       "@context": "http://schema.org",
@@ -110,6 +113,11 @@
   {% endif %}
 {% endif %}
 
+{% if site.facebook %}
+  <meta property="article:publisher" content="{{ site.facebook.publisher }}" />
+  <meta property="fb:app_id" content="{{ site.facebook.app_id }}" />
+{% endif %}
+
 {% if site.logo %}
   <script type="application/ld+json">
     {