LibWeb: Implement the <style> SVG element

The `<style>` element is allowed to be in the SVG namespace, so we now
support this element.

It has the same behaviour as the HTML namespace `<style>` element as
described in the spec.

"The semantics and processing of a ‘style’ and its attributes must be
the same as is defined for the HTML ‘style’ element."

Userland/Libraries/LibWeb/SVG/SVGStyleElement.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2023, Preston Taylor <PrestonLeeTaylor@proton.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/DOM/StyleElementUtils.h>
+#include <LibWeb/SVG/SVGElement.h>
+
+namespace Web::SVG {
+
+class SVGStyleElement final : public SVGElement {
+    WEB_PLATFORM_OBJECT(HTMLStyleElement, SVGElement);
+
+public:
+    virtual ~SVGStyleElement() override;
+
+    virtual void children_changed() override;
+    virtual void inserted() override;
+    virtual void removed_from(Node*) override;
+
+    CSS::CSSStyleSheet* sheet();
+    CSS::CSSStyleSheet const* sheet() const;
+
+private:
+    SVGStyleElement(DOM::Document&, DOM::QualifiedName);
+
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
+    virtual void visit_edges(Cell::Visitor&) override;
+
+    // The semantics and processing of a ‘style’ and its attributes must be the same as is defined for the HTML ‘style’ element.
+    DOM::StyleElementUtils m_style_element_utils;
+};
+
+}