LibWeb: Make CSSRule and all its subclasses GC-allocated

Author: https://github.com/awesomekling
Commit: 12042f0757
Pull-request: https://github.com/SerenityOS/serenity/pull/14816
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/CSS/CSSStyleRule.idl

@@ -1,6 +1,7 @@
 #import <CSS/CSSRule.idl>
 #import <CSS/CSSStyleDeclaration.idl>
 
+[Exposed=Window, NoInstanceWrapper]
 interface CSSStyleRule : CSSRule {
 
     attribute CSSOMString selectorText;