Implement channel ApplicationCommandPermissionTarge

src/Discord.Net.Core/Entities/Permissions/ApplicationCommandPermissionTarget.cs

@@ -12,6 +12,10 @@ namespace Discord
         /// <summary>
         ///     The target of the permission is a user.
         /// </summary>
-        User = 2
+        User = 2,
+        /// <summary>
+        ///     The target of the permission is a channel.
+        /// </summary>
+        Channel = 3
     }
 }