docs: Configuration, known_hosts - is a little light.

[CarlFK]

This might be a debian packing problem, but the docs for this one item seem to be missing a bit.

https://github.com/daradib/sidedoor#configuration

known_hosts: SSH host key of the remote server.

it would be nice to know what dir and permissions, and how to get the key using ssh-keyscan.

[e-gaulue]

I agree 👍