docs/os-updates: Various tweaks/modernization
docs/os-updates: Various tweaks/modernization

Mention the fact that it's also `atomic host`, and the deploy command,
a bit more information about remotes and origins, etc.

nzwulfin/atomic-site,bexelbie/atomic-site,bexelbie/atomic-site,bexelbie/atomic-site,nzwulfin/atomic-site,nzwulfin/atomic-site,bexelbie/atomic-site,nzwulfin/atomic-site,nzwulfin/atomic-site,bexelbie/atomic-site