Rename close icon to close button (#29387)

site/content/docs/4.3/components/close-button.md

@@ -0,0 +1,14 @@
+---
+layout: docs
+title: Close button
+description: A generic close button for dismissing content like modals and alerts.
+group: components
+---
+
+**Be sure to include text for screen readers**, as we've done with `aria-label`.
+
+{{< example >}}
+<button type="button" class="close" aria-label="Close">
+  <span aria-hidden="true">&times;</span>
+</button>
+{{< /example >}}