Docs: Breaks out Utilities into separate section and optimizes its pages (#20678)

docs/_includes/page-headers.html

@@ -18,6 +18,11 @@
   <p class="lead">
     Over a dozen reusable components built to provide buttons, dropdowns, input groups, navigation, alerts, and much more.
   </p>
+{% elsif page.group == "utilities" %}
+  <h1>Utilities</h1>
+  <p class="lead">
+    Bootstrap includes dozens of utilities—classes with a single purpose to reduce the frequency of highly repetitive declarations.
+  </p>
 {% elsif page.group == "javascript" %}
   <h1>JavaScript plugins</h1>
   <p class="lead">