LibWeb: Invalidate the layout tree on DOM node insertion

Author: https://github.com/awesomekling
Commit: 3cea86632d
Pull-request: https://github.com/SerenityOS/serenity/pull/19275
Reviewed-by: https://github.com/gmta ✅

Userland/Libraries/LibWeb/DOM/Node.cpp

@@ -487,6 +487,8 @@ void Node::insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, boo
 
     // FIXME: This will need to become smarter when we implement the :has() selector.
     invalidate_style();
+
+    document().invalidate_layout();
 }
 
 // https://dom.spec.whatwg.org/#concept-node-pre-insert