Add a callout for the search role

site/content/docs/5.1/components/navbar.md

@@ -235,6 +235,12 @@ Immediate child elements of `.navbar` use flex layout and will default to `justi
 </nav>
 {{< /example >}}
 
+{{< callout warning >}}
+#### Ensure correct search `role`
+
+In order for assistive technologies (such as screen readers) to identify a section of the page used to search content, the form should have a `role=search`.
+{{< /callout >}}
+
 Input groups work, too. If your navbar is an entire form, or mostly a form, you can use the `<form>` element as the container and save some HTML. Applies to the option above and below this copy.
 
 {{< example >}}