Add skeleton for ISO9660 read-only implementation.

DiscImageChef.Filesystems/ISO9660/Super.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using DiscImageChef.CommonTypes;
+using DiscImageChef.CommonTypes.Interfaces;
+using DiscImageChef.CommonTypes.Structs;
+
+namespace DiscImageChef.Filesystems.ISO9660
+{
+    public partial class ISO9660
+    {
+        public Errno Mount(IMediaImage                imagePlugin, Partition partition, Encoding encoding,
+                           Dictionary<string, string> options,     string    @namespace) =>
+            throw new NotImplementedException();
+
+        public Errno Unmount() => throw new NotImplementedException();
+
+        public Errno StatFs(out FileSystemInfo stat) => throw new NotImplementedException();
+    }
+}