LibWeb: Add and implement CSSPropertyRule IDL and bindings

Author: https://github.com/a-ungurianu 🔰
Commit: 50d64b0fb7
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1777
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/AtkinsSJ ✅

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -2694,6 +2694,7 @@ void StyleComputer::build_qualified_layer_names_cache()
             case CSSRule::Type::Namespace:
             case CSSRule::Type::NestedDeclarations:
             case CSSRule::Type::Supports:
+            case CSSRule::Type::Property:
                 break;
             }
         });