_includes/head/seo/opengraph.html

    <meta property="og:title" content="{{ seo_title }}">
    <meta property="og:description" content="{{ seo_description }}">
    <meta property="og:type" content="{{ seo_type }}">
    <meta property="og:url" content="{{ site.github.url }}{{ page.url }}">
    <meta property="og:image" content="{{ seo_image }}">
    <meta property="fb:app_id" content="{{ site.seo.facebook.app_id }}">