Adds next and previous post links.

_includes/layouts/post.njk

@@ -6,4 +6,10 @@ templateClass: tmpl-post
 
 {{ content | safe }}
 
-<p><a href="{{ '/' | url }}">← Home</a></p>
+<hr>
+<ul>
+  {%- set nextPost = collections.posts | getNextCollectionItem(page) %}
+  {%- if nextPost %}<li>Next: <a href="{{ nextPost.url | url }}">{{ nextPost.data.title }}</a></li>{% endif %}
+  {%- set previousPost = collections.posts | getPreviousCollectionItem(page) %}
+  {%- if previousPost %}<li>Previous: <a href="{{ previousPost.url | url }}">{{ previousPost.data.title }}</a></li>{% endif %}
+</ul>