Add step and preface section includes

_includes/docs-preface.html

@@ -0,0 +1,11 @@
+<div class="d-lg-flex gap-x-4" {% if include.reverse %}style="flex-direction: row-reverse"{% endif %}>
+  <div style="flex: 1">
+    {{ include.title | markdownify }}
+    {{ include.content | markdownify }}
+  </div>
+  {% if include.image %}
+  <div style="flex: 1">
+    <img src="{{ include.image }}" alt="{{ include.alt }}">
+  </div>
+  {% endif %}
+</div>