chore: Fixes props validator issue with CBotton component, when size set to "xs".

Author: kurotanshi

packages/chakra-ui-core/src/CButton/utils/button.props.js

@@ -33,7 +33,7 @@ export const buttonProps = {
   size: {
     type: String,
     default: 'md',
-    validator: value => value.match(/^(sm|md|lg)$/)
+    validator: value => value.match(/^(xs|sm|md|lg)$/)
   },
   loadingText: {
     type: String,