Add an optional featured image (#252)

Bobby

27.46.2020 be94b5fd052b910d0b3704bea22d26214136f060

 layouts/posts/single.html

@@ -27,9 +27,13 @@
      </header>

      <div>
        {{ if .Params.featured_image }}
          <img src='{{ .Params.featured_image }}' alt="Featured image"/>
        {{ end }}
        {{ .Content }}
      </div>


      <footer>
        {{ partial "posts/series.html" . }}
        {{ partial "posts/disqus.html" . }}