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

docs/utilities/image-replacement.md

@@ -0,0 +1,18 @@
+---
+layout: docs
+title: Image replacement
+group: utilities
+---
+
+Utilize the `.text-hide` class or mixin to help replace an element's text content with a background image.
+
+{% highlight html %}
+<h1 class="text-hide">Custom heading</h1>
+{% endhighlight %}
+
+{% highlight scss %}
+// Usage as a mixin
+.heading {
+  @include text-hide;
+}
+{% endhighlight %}