Add -ssh: an opt-in built-in SSH server (public keys only, sessions only)

go.sum

@@ -2,6 +2,8 @@ git.veillax.com/Veillax/reef v0.1.11 h1:kbjgxJpmpp1HRckbW1tqJUm5/ftgvSlmUHAhFXug
 git.veillax.com/Veillax/reef v0.1.11/go.mod h1:ZBUd/BARO5kkpUNTP81TTY1aQXLHFR6bKDhCxckjHso=
 github.com/Microsoft/go-winio v0.6.4 h1:kJF2pamtYCWXf0xAT8sAkwKC0pMl2HYBrRPHAqyUc+g=
 github.com/Microsoft/go-winio v0.6.4/go.mod h1:1xl5JXG4ze/m74GH6Dc4Mwxfc3VL5siRVQjIAlHH07U=
+github.com/creack/pty v1.1.24 h1:bJrF4RRfyJnbTJqzRLHzcGaZK1NeM5kTC9jGgovnR1s=
+github.com/creack/pty v1.1.24/go.mod h1:08sCNb52WyoAwi2QDyzUCTgcvVFhUzewun7wtTfvcwE=
 github.com/google/btree v1.1.2 h1:xf4v41cLI2Z6FxbKm+8Bu+m8ifhj15JuZ9sa0jZCMUU=
 github.com/google/btree v1.1.2/go.mod h1:qOPhT0dTNdNzV6Z/lhRX0YXUafgPLFUh+gZMl761Gm4=
 golang.org/x/crypto v0.58.0 h1:COkYLr4k7nDI4r6QtMML2AfzeIswWHAJthLS6K/M/54=