fix: Merge pull request #22252 from unoplatform/copilot/sub-pr-22211

fix: Add missing sass:color import for lighten() function in alerts.scss

Author: Jen-Uno

doc/templates/uno/component/alerts.scss

@@ -1,3 +1,4 @@
+@use 'sass:color';
 @use '../variables' as *;
 
 .alert {