Add to changelog

Author: lachlanjc

CHANGELOG.md

@@ -15,6 +15,7 @@
 - Global color mode styles are automatically added to the body without needing to render the `ColorMode` component
 - Removes `ThemeStateProvider`
 - Adds global typographic styles, set `useBodyStyles: false` to disable
+- Adds support for combining multiple variants (pass `variants` an array in `sx` or as a prop on components)
 - Fix issue where `<del>` tag was incorrectly specified as `delete`
 
 ## v0.2.53 2019-12-19