feat: add modern content and navigation primitives

layouts/shortcodes/step.html

@@ -0,0 +1,7 @@
+{{ $title := .Get "title" | default "Step" }}
+{{ $number := .Get "number" }}
+<li class="relative">
+  <span class="absolute -start-[2.1rem] top-0 flex h-8 w-8 items-center justify-center rounded-full bg-primary-600 text-sm font-black text-white ring-4 ring-neutral dark:ring-neutral-800">{{ $number | default "•" }}</span>
+  <h3 class="text-lg font-bold text-neutral-950 dark:text-white">{{ $title | markdownify }}</h3>
+  <div class="mt-1 text-neutral-600 dark:text-neutral-400">{{ .Inner | markdownify }}</div>
+</li>