Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibHTML/CSS/StyleSheet.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <AK/NonnullRefPtrVector.h>
+#include <LibHTML/CSS/StyleRule.h>
+
+class StyleSheet : public RefCounted<StyleSheet> {
+public:
+    static NonnullRefPtr<StyleSheet> create(NonnullRefPtrVector<StyleRule>&& rules)
+    {
+        return adopt(*new StyleSheet(move(rules)));
+    }
+
+    ~StyleSheet();
+
+    const NonnullRefPtrVector<StyleRule>& rules() const { return m_rules; }
+
+private:
+    explicit StyleSheet(NonnullRefPtrVector<StyleRule>&&);
+
+    NonnullRefPtrVector<StyleRule> m_rules;
+};