Implement ED25519

[drpeterfranz]

Ubuntu 22.04 which is now the default distro by AWS no longer accepts the RSA keys which worked absolutely fine with previous versions. Instead the newer ED25519 key is required, but that is not implemented in QSsh yet. I would offer to add this to the repo myself but I have absolutely no clue about how to do this.

Would it be either possible for you to do this, or if you're too busy could you send me instructions on how to do this? It's the cryptography side of which I have no idea how it works, but I could do the implementation if I knew the necessary basic steps.