Add tom-key-update file.

Add tom-key-update file.

I'm transitioning to a new SSH key, because I upgrade my SSH key to
ed25519 instead of my old key was compromised. I hope a system
administrator can help me to update the key.

To prove I have the old key to access this repository, I commit that
statement on this repository and push it to the remote repository. Sorry
to bothering someone who irrelevant to this, I may remove this statement
after a system administrator updated my SSH key.