add related posts and update some styling

_includes/layouts/post.njk

@@ -3,6 +3,7 @@ layout: base.njk
 ---
 {% css %}{% include "css/post.css" %}{% endcss %}
 {% css %}{% include "css/highlighting.css" %}{% endcss %}
+{% css %}{% include "css/lists.css" %}{% endcss %}
 {% js %}{% include "node_modules/@zachleat/heading-anchors/heading-anchors.js" %}{% endjs %}
 
 <heading-anchors content="<i class='fa-solid fa-anchor'></i>">
@@ -43,4 +44,16 @@ layout: base.njk
   {% set newerTitle = newerPost.data.title %}
   {% set inPost = true %}
   {% include "pagination.njk" %}
+
+  <hr>
+
+  {% set relevantTags = tags | removeBasicTags %}
+  {% set postlist = collections.posts | filterByTags(relevantTags) | excludeFromCollection([page.url, olderHref, newerHref]) | randomize | head(3) %}
+  {% if postlist.length %}
+  <section class="related-posts">
+    <h2>related posts</h2>
+    {% include "postlist.njk" %}
+  </section>
+  {% endif %}
+
 </heading-anchors>