RFC: Upstream Forgejo/Gitea support

[openscript]

Hi! We are using Changesets successfully across Codeberg and self-hosted Forgejo instances. The only component requiring adjustments for Gitea/Forgejo API compatibility is this action.

I have already implemented and tested these changes in a fork:
https://github.com/openscript/changesets-action

Key points:

• Fully backward compatible with GitHub (no changes to existing workflows).
• Enables Changesets for Forgejo, Gitea, and Codeberg users.

Would you be open to a PR merging this upstream? Happy to open one and adapt the implementation to your preferred patterns.

[Andarist]

It would be good if u’d post a list of changes that you had to introduce to add that support

[openscript]

Changes I needed to introduce:

• Platform detection: https://github.com/openscript/changesets-action/blob/1967829df87d04313e295397cc26365b1c2c1eba/src/run.ts#L28-L34
• List pull requests (manual filtering by head and base, because not supported via REST API): https://github.com/openscript/changesets-action/blob/1967829df87d04313e295397cc26365b1c2c1eba/src/run.ts#L62-L79
• Update pull request via REST (not supported via Graphql): https://github.com/openscript/changesets-action/blob/1967829df87d04313e295397cc26365b1c2c1eba/src/run.ts#L512-L523

[bluwy]

The changes seem acceptable to me, looks like it's mainly handling the octokit api differences and not a lot of maintenance overhead. But we'll likely need community maintenance for this later on as we don't use forgejo or gitea to be able to test this.

We also use https://github.com/changesets/ghcommit in pushChanges which I assume is working fine too? It uses a fair amount of octokit api itself.