LibWeb: Add CSSRuleList

"The CSSRuleList interface represents an ordered collection of CSS style
rules." - https://www.w3.org/TR/cssom-1/#the-cssrulelist-interface

Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/CSS/CSSRuleList.h>
+
+namespace Web::CSS {
+
+CSSRuleList::CSSRuleList(NonnullRefPtrVector<CSSRule>&& rules)
+    : m_rules(rules)
+{
+}
+
+CSSRuleList::~CSSRuleList()
+{
+}
+
+}