Document in CHANGELOG

CHANGELOG.md

@@ -63,6 +63,19 @@ Do not include an empty `<span class="govuk-summary-list__actions"></span>` with
 
 This change was introduced in [pull request #2323: Avoid invalid nesting of `<span>` within a `<dd>` in summary list](https://github.com/alphagov/govuk-frontend/pull/2323).
 
+#### Update the HTML for navigation in the header
+
+We've updated the HTML for the header. This update only affects you if your header includes navigation.
+
+If you are not using Nunjucks macros then you should:
+
+- move the `<button>` inside the `<nav>`, immediately before the `<ul>`
+- move the `aria-label` from the `<ul>` to the `<nav>`
+
+Check your changes against [the example in the Design System](https://design-system.service.gov.uk/components/header/#header-with-service-name-and-navigation).
+
+This change was introduced in [pull request #2427: Improvements to the screen reader experience for the menu in the header](https://github.com/alphagov/govuk-frontend/pull/2427).
+
 #### Make sure components that conditionally reveal other questions still work as expected
 
 On radios and checkboxes, the JavaScript now looks within the whole page for conditionally revealed content. Before, it only looked within the same set of radios or checkboxes.