[idea] Shell completion for --remote targets

[yufo211]

idea / problem

herdr --remote <TAB> doesn't suggest any hosts. Right now it completes
filenames from the current directory instead.

I normally connect over ssh using the Host aliases in my ~/.ssh/config,
so I keep reaching for the same muscle memory with herdr and end up typing
the hostname out in full every time.

requested change

I'd like shell completion to work for the --remote value.

Host aliases from ~/.ssh/config would be the most useful candidates,
since that's how I actually connect.

why you want this

Typing the hostname by hand every time I connect to a remote server for
development is a small but constant bit of friction. If completion worked
the way it does for the ssh command, that would go away.