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

docs/utilities/screenreaders.md

@@ -0,0 +1,23 @@
+---
+layout: docs
+title: Screenreaders
+group: utilities
+---
+
+Hide an element to all devices **except screen readers** with `.sr-only`. Combine `.sr-only` with `.sr-only-focusable` to show the element again when it's focused (e.g. by a keyboard-only user). Can also be used as mixins.
+
+{% comment %}
+Necessary for following [accessibility best practices](../getting-started/#accessibility).
+{% endcomment %}
+
+{% highlight html %}
+<a class="sr-only sr-only-focusable" href="#content">Skip to main content</a>
+{% endhighlight %}
+
+{% highlight scss %}
+// Usage as a mixin
+.skip-navigation {
+  @include sr-only;
+  @include sr-only-focusable;
+}
+{% endhighlight %}