Jekyll plugin to add metadata tags

 Jekyll SEO Tag adds the following meta tags to the site:
 .
   * Page title, with site title or description appended
   * Page description
   * Canonical URL
   * Next and previous URLs on paginated pages
   * JSON-LD Site and post metadata for richer indexing
   * Open Graph title, description, site title, and URL
   * Twitter Summary Card metadata
 .
 While one could theoretically add the necessary metadata tags oneself,
 Jekyll SEO Tag provides a battle-tested template of crowdsourced
 best-practices.