Update changelog

Author: planktonic

CHANGELOG.md

@@ -22,6 +22,7 @@
 - Updated the default configuration for typography. If you want to keep the old typographic scale (font-sizes and line-heights), you can re-instate the old configuration.
 - Default visual appearance of Atoms/Dropdown component has been updated. If you were already overriding this, you may see no difference
 - Bitstyles can no longer be imported using Sass’s `@import` statements — you’ll need to either switch to using `@use` statements, or use bitstyles v5.0.1.
+- Renames the `.o-ui-group` component to `.o-joined-ui`, and removes the need for extra child classes on your elements. You’ll need to replace all instances of `.o-ui-group` with `o-joined-ui`, and remove all instances of `.o-ui-group__item`, `.o-ui-group__first`, and `.o-ui-group__last`. Any instances of `u-border-radius-0` classes on these components must also be removed, as this is now handled in pure CSS.
 
 ### Added