Add related content section to single page (#77)

Set `relatedPosts` to `true` in the config to enable this.

layouts/posts/single.html

@@ -25,6 +25,9 @@
 			<div class="content">
 				{{ .Content | replaceRE "(<h[1-6] id=\"([^\"]+)\".+)(</h[1-6]+>)" `${1}<a href="#${2}" class="anchor" aria-hidden="true"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M15 7h3a5 5 0 0 1 5 5 5 5 0 0 1-5 5h-3m-6 0H6a5 5 0 0 1-5-5 5 5 0 0 1 5-5h3"></path><line x1="8" y1="12" x2="16" y2="12"></line></svg></a>${3}` | safeHTML }}
 			</div>
+			{{- if .Site.Params.relatedPosts }}
+			{{- partial "related-posts.html" . -}}
+			{{- end }}
 			<hr class="post-end">
 			<footer class="post-info">
 				{{- with .Params.tags }}