feat: style layers, imports and nesting

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

@@ -1,9 +1,5 @@
 {% 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 be out of date.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>