Add a "remote_priority" configuration option

[ahal]

Is your feature request related to a problem? Please describe.
I tend to point the origin remote at my personal forks, then create an upstream remote to point at the canonical repo. I'd like a way to be able to use the upstream remote if it exists, but fallback to origin if it doesn't.

Describe the solution you'd like
A new configuration called remote_priority could be used. This would be an array that specifies the remotes in order of preference they should be used. E.g:

remote_priority = {"upstream", "origin"}

This would default to an empty array. When determining the user specified remote to use, we'd first iterate over all remotes in this list and return the first one that exists. If no remotes exist (or the array is empty), we'd use opt.remote as usual.

Additional context
I may be willing to work on this feature if it's something you'd accept.

[linrongbin16]

hi @ahal , selection in multiple remote upstreams is supported in: https://github.com/linrongbin16/gitlinker.nvim.

Also see: #91 .