LibWeb: Add fast way to check if a DOM node is an SVG element

Author: https://github.com/awesomekling
Commit: dd19f61538
Pull-request: https://github.com/SerenityOS/serenity/pull/19006

Userland/Libraries/LibWeb/DOM/Node.h

@@ -73,6 +73,7 @@ public:
 
     virtual bool requires_svg_container() const { return false; }
     virtual bool is_svg_container() const { return false; }
+    virtual bool is_svg_element() const { return false; }
     virtual bool is_svg_svg_element() const { return false; }
 
     bool in_a_document_tree() const;