[Feature request] Document use with sudo

[simcop2387]

Is your feature request related to a problem? Please describe.

The program is somewhat more a generic authentication check than ssh specific, so I've actually integrated it into the sudo pam.d files so that it can be used to authenticate users with sudo the same way that it works for ssh.

Describe the solution you'd like

I will document how this worked for me on debian and ubuntu, and then this would let users to not need a local password for each machine to be able to use sudo (in whatever way is configured). This would mean that users who you want to be able to say manage systemd services could be given access to commands and use the same keycloak password and otp setup that they use for ssh.