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/StyleRule.cpp

@@ -0,0 +1,11 @@
+#include <LibHTML/CSS/StyleRule.h>
+
+StyleRule::StyleRule(Vector<Selector>&& selectors, NonnullRefPtrVector<StyleDeclaration>&& declarations)
+    : m_selectors(move(selectors))
+    , m_declarations(move(declarations))
+{
+}
+
+StyleRule::~StyleRule()
+{
+}