LibHTML: Add a simple <style> element for inline CSS

Libraries/LibHTML/DOM/HTMLStyleElement.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <LibHTML/DOM/HTMLElement.h>
+
+class StyleSheet;
+
+class HTMLStyleElement : public HTMLElement {
+public:
+    HTMLStyleElement(Document&, const String& tag_name);
+    virtual ~HTMLStyleElement() override;
+
+    virtual void inserted_into(Node&) override;
+    virtual void removed_from(Node&) override;
+
+private:
+    RefPtr<StyleSheet> m_stylesheet;
+};