[Feature Request] Add Open Authoring Support with GitHub Fork + PR Workflow (Like DecapCMS)

Hi Keystatic team! 👋

First off, thank you for building such a modern, thoughtful CMS. The GitHub-backed approach is awesome for developer workflows and content versioning.

However, one major feature currently missing — and very useful for community-driven projects — is Open Authoring, like what [DecapCMS](https://decapcms.org/docs/open-authoring/) supports.

💡 What is Open Authoring?

Open authoring allows contributors who aren’t collaborators on a GitHub repository to:

• Authenticate via GitHub
• Automatically fork the repo to their own account
• Create a branch and edit content in the CMS UI
• Submit a Pull Request back to the main repo
• All without using Git or needing write access

This enables non-technical contributors (like writers, translators, editors) to easily contribute through a visual interface, while maintaining version control and review workflows.

🎯 Why This Is Important

For open-source or community knowledge bases (e.g. multilingual projects, documentation, religious or educational content), open authoring is a game-changer. Contributors can submit translations or updates without technical friction.

We’d love to use Keystatic for such a project, but this feature is a blocker. Otherwise, we’d need to keep using DecapCMS for now just to enable this flow.

✅ Suggested Features

• Auto-fork GitHub repo if the user is not a collaborator
• Let users edit content via Keystatic UI on a new branch
• Submit a PR to the original repo
• Optional: Approvals from maintainers, notifications, etc.

📦 Example Use Cases

• Open documentation sites
• Multilingual content contributions
• Public religious/educational repositories (e.g. Seerah content, where anyone can contribute translation or lessons)

🙏 Thank you!

Keystatic is amazing already. This one feature would make it perfect for many community-first projects.

Looking forward to your thoughts!

The issue names no files, tests, or entry points. Start by tracing Keystatic’s existing GitHub authentication and content-editing flow, then compare the requested fork, branch, and PR lifecycle with DecapCMS’s open-authoring documentation; done means an agreed design and working end-to-end workflow for non-collaborators.