[Feature Request] Support multiple domain shorteners

[frandj99]

Hi, I would like to ask if it will be possible to have an option for select what domain use with the shortner extension.
I have 2 domains with 2 different YOURLS installation (and probably I'm gonna add a 3rd too) so I would like to have something like a dropdown menu for select which domain use for short the URL everytime.
I guess this would need different signatures for every servers.

Thanks in advance if you could add this feature