Use ed25519 for SSH keys

[haobibo]

Code: https://github.com/QPod/lab-dev/blob/main/docker_devbox/work/start--pre.sh#L5

Change to: ssh-keygen -t ed25519 -N "" -C hostname -f -f ~/.ssh/id_ed25519

ref: https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent#generating-a-new-ssh-key

[haobibo]

Fixed in #31