Post SSH host key on initial login page

[hblanks]

It may be a good idea to post the current SSH host key (fingerprints and pubkeys as you'd append to known_hosts) on some early part of the (HTTPS) onboarding process. The paranoid (and people automating SSH from some machine) will thank you.

$ ssh cmd.io 
The authenticity of host 'cmd.io (34.196.61.179)' can't be established.
RSA key fingerprint is SHA256:q/p5ECt4eMRCnLNFLtB0uDr61Q7NdE6aNHDWHvy9ibg.
Are you sure you want to continue connecting (yes/no)?  

[progrium]

Great idea. We can put this in the docs for now and then when we have a proper onboarding path we can make sure it's a part of that.