Add zip1.io url shortening service

[PhoenixOnARoof]

Hello. This PR serves to add a third url shortening service "zip1.io" to the site because the existing "v.gd" and "ulvis.net" options regularly don't work

[taleden]

I appreciate the contribution! But, since EDSY currently relays shortlink creation and expansion through the server, I think it's always going to hit zip1.io's rate limit. For now I think I'm going to have to go the opposite way and remove shortlink integration until I have time to redesign it to be client side, or set up an EDSY/EDCD-hosted solution.

[taleden]

Per your comment on discord, yeah, I must've misread the rate limit docs. I guess it's worth trying one more free third party generator, although I suspect we'll be right back in this situation before long. =D Thanks for the patch!