Document in changelog

CHANGELOG.md

@@ -8,12 +8,30 @@
 
 We darkened `govuk-colour("dark-grey")` to improve the readability of hint text. It now has a contrast ratio of 7:1 and helps hint text meet the WCAG 2.1 (AAA) accessibility standard.
 
+#### Updated error styling for form controls
+
+We've changed the error styling for form controls so that the border no longer get thicker. We're making this change to ensure that the focus state is always perceivable.
+
+When an error message relates to multiple fields, ensure you are explicit about which field has the error. You must not rely on users being able to perceive which field has the error styling.
+
+([PR #1870](https://github.com/alphagov/govuk-frontend/pull/1870))
+
 #### Add spellcheck parameter to input and textarea components
 
 Optional parameter added to the input and textarea components to enable or disable the spellcheck attribute
 
 ([PR #1859](https://github.com/alphagov/govuk-frontend/pull/1859))
 
+### Deprecated features
+
+#### The `$govuk-border-width-form-element-error` setting
+
+The `$govuk-border-width-form-element-error` setting has been deprecated, and will be removed in GOV.UK Frontend v4.0.
+
+Update any references to `$govuk-border-width-form-element-error` in your application's styles to reference `$govuk-border-width-form-element` instead.
+
+([PR #1870](https://github.com/alphagov/govuk-frontend/pull/1870))
+
 ### Fixes
 
 We’ve made fixes to GOV.UK Frontend in the following pull requests: