Add ruleset and skin resource stub.

Assets/Cryville/Crtr/Skin.cs

@@ -1,5 +1,6 @@
 using Cryville.Common;
 using Cryville.Common.Pdt;
+using Cryville.Crtr.Browsing;
 using Cryville.Crtr.Components;
 using Newtonsoft.Json;
 using System;
@@ -10,7 +11,7 @@ using System.Reflection;
 using System.Text;
 
 namespace Cryville.Crtr {
-	public class Skin {
+	public class Skin : MetaInfo {
 		[JsonRequired]
 		public long format;