LibWeb: Parse the CSS scrollbar-width property

Author: https://github.com/kalenikaliaksandr
Commit: 8d9e20cb03
Pull-request: https://github.com/SerenityOS/serenity/pull/23381
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/trflynn89 ✅

Userland/Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -1110,4 +1110,10 @@ QuotesData StyleProperties::quotes() const
     return InitialValues::quotes();
 }
 
+Optional<CSS::ScrollbarWidth> StyleProperties::scrollbar_width() const
+{
+    auto value = property(CSS::PropertyID::ScrollbarWidth);
+    return value_id_to_scrollbar_width(value->to_identifier());
+}
+
 }