Rot13 Spoiler Command

I know there has been some push for spoiler markdown, but what I suggest would be a bit simpler, I feel. Rot13 is a simple rotation cipher, commonly used for spoilers. The command would either be /rot13 <message> and simply do the default letter rotation, or it could be /rot <number> <message> and let you encode it with whatever number you want. How the rotation cipher works, if it is not already obvious, is it takes each letter in a message, and it changes it <number> times down the alphabet, looping back to A at Z. So a Rot1 cipher would change A to B, B to C, and Z to A. I hope that this gets considered, as I believe it would be a great help in keeping chats spoiler free.