Support Forgejo (e.g., Codeberg)

[tarsius]

I am a Guix user and am excited that Guix is moving to Codeberg, and of course I want to use Forge with that. Adding support for Forgejo is now something I plan to do, no longer something that I might eventually end up doing, should I ever run out of other more urgent work.

That being said I still do not intend to drop everything else and work on Forgejo support instead. I have already committed to do other work first, which is going to take me at least two months. Please do not pressure me to do it earlier, as that would turn something that I am excited about, into something that makes me anxious, and that would cause a delay.

I also do not intend to merge someone else's implementation, because that would add to the technical dept, and my plan is to pay off some dept first, not take on more. It appears that some Guix folks intend to maintain a fork of Forge with Codeberg support, until I get around to adding official support. I don't think that's published yet, but keep an eye on https://packages.guix.gnu.org/packages/emacs-forge/.

Since Forgejo is a fork of Gitea, which is a fork of Gogs, adding support for the latter two might not be that much work once Forgejo is supported. So that is on the table again too.