[qutebrowser] Per-domain editor.command, or equivalent

[David Nebauer]

Excerpts from Jay Kamat's message of January 6, 2019 8:20 am:
> 
> I already said this in the issue you posted, but I think the cleanest
> solution for this is to add url pattern support to editor.command directly.

I wholeheartedly agree. As I posted in the issue, I have been able to 
come up with a workaround bound to another key, but it is an unholy 
kludge. I understand that per-domain editor commands may not be a common 
need, but surely I'm not the only one with a legitimate use case for it.

Thanks for your advice on this.

-David