LibWeb: Sketch out a very basic SVG <clipPath> element

This element doesn't actually support anything at the moment, but it
still massively speeds up painting performance on Wikipedia! :^)

How? Because we no longer paint SVG <path> elements found inside
<clipPath> elements. SVGClipPathElement::create_layout_node() returns
nullptr which stops the layout tree builder from recursing further into
the subtree, and so the <path> element never gets a layout or paint box.

Mousing over Wikipedia now barely break 50% CPU usage on my machine :^)

Userland/Libraries/LibWeb/SVG/SVGClipPathElement.cpp

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/SVG/SVGClipPathElement.h>
+
+namespace Web::SVG {
+
+SVGClipPathElement::SVGClipPathElement(DOM::Document& document, DOM::QualifiedName qualified_name)
+    : SVGElement(document, move(qualified_name))
+{
+}
+
+SVGClipPathElement::~SVGClipPathElement()
+{
+}
+
+RefPtr<Layout::Node> SVGClipPathElement::create_layout_node(NonnullRefPtr<CSS::StyleProperties>)
+{
+    return nullptr;
+}
+
+}