Allow to use other Git hosts for "GitHub Links"

As highlighted in the discussion below, it would be great to allow users to use GitLab, BitBucket, Gitea, for the "GitHub Links", and not only GitHub.

Discussed in https://github.com/quarto-dev/quarto-cli/discussions/5281

^{Originally posted by christophsax April 23, 2023}
In Quarto, there is the lovely feature that directly links to the edit page on GitHub. At first glance, this seems to work for other platforms, such as Gitea, as well. However, quarto points to edit, Gitea expects it at _edit.

Is there any way the edit link can be tweaked?

This is where Quarto links to: .../edit/main/index.qmd
This is how a Gitea edit link looks like: .../_edit/main/index.qmd

Start with discussion 5281 and the existing “GitHub Links” entry point that builds edit URLs; the payload names no source file or test. Compare the URL conventions described for GitLab, BitBucket, and Gitea. Done means users can use those hosts, including Gitea’s _edit path rather than only GitHub’s edit path.