feat: add SSH known hosts prompt handling

[Chayanon-Ninyawee]

Add SSH known hosts prompt handling and user confirmation

Check for existing host keys, show fingerprint prompt, and add keys on approval

If the host is not in the known-hosts it will show:

The authenticity of host '192.168.239.10' can't be established.
256 SHA256:YULIwdfuCLci7fxALmON53lsJT3bC7CemoE/OY/BcZc 192.168.239.10 (ED25519)
Add this host key to /home/garfieldcmix/.ssh/known_hosts?
 y/n:

Also added:

connections = {
  ...
  ssh_known_hosts = vim.fn.expand "$HOME" .. "/.ssh/known_hosts",
  ...
},

[nosduco]

Awesome stuff! Would you mind updating the README to include those changes? Or I can go ahead and do that. Thanks again for your contributions!