feat: design + perf + tags etc.

src/_includes/partials/banners/old-post.liquid

@@ -0,0 +1,10 @@
+{% assign isOldPost = date | oldPost %}
+{% if isOldPost %}
+  {% capture css %}
+    {% render "../../../assets/styles/components/banners.css" %}
+  {% endcapture %}
+  <style>{{ css }}</style>
+  <div class="banner old-post">
+    <p>{% tablericon "clock-x" "Old post" %} This post is over 3 years old. I've probably changed my mind since it was written and it <em>could</em> be out of date.</p>
+  </div>
+{% endif %}