refactor: extract a Callout component

src/components/Callout.astro

@@ -0,0 +1,15 @@
+---
+interface Props {
+  title: string;
+}
+
+const { title } = Astro.props as Props;
+---
+
+<aside
+  class="p-6 my-8 border border-gray-300 dark:bg-gray-800 dark:border-gray-700"
+>
+  <h2 class="mt-0">{title}</h2>
+
+  <slot />
+</aside>