LibWeb: Implement the color-scheme meta tag name

Author: https://github.com/Gingeh
Commit: df70455d3f
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3146
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/HTML/HTMLMetaElement.h

@@ -41,8 +41,12 @@ private:
 
     virtual void initialize(JS::Realm&) override;
 
+    void update_metadata(Optional<String> const& old_name = {});
+
     // ^DOM::Element
     virtual void inserted() override;
+    virtual void removed_from(Node*) override;
+    virtual void attribute_changed(FlyString const& local_name, Optional<String> const& old_value, Optional<String> const& value, Optional<FlyString> const& namespace_) override;
 };
 
 }