[Feature Request] Add configurable Gitea instances

[f0sh]

What problem does the feature solve?

The Gitea Software can be used also as a self-hosted solution. There are big, open to public Gitea instances like Codeberg. They all usually share the same API as gitea.com and therefore make it feasable to use as a provider for vssue. Therefore the hardcoded URL in vssue.gitea.min.js must be configurable.

Proposed solution

Add a new configuration option location which takes an url like https://codeberg.org to add the location of the Gitea instance.

Alternative solutions

none