Reintroduce standalone docs repo with live sync and versioned branches

[0xAvium]

Abstract:

After testing HydePHP with Cursor in agent mode, it performed surprisingly well even with limited documentation. We had removed the standalone docs repo previously, but this highlighted how useful it would be to have it back in place, especially for offline use and automated tools.

Plan:

• Restore the docs repository as a separate, dedicated repo.
• Set up live syncing from the main monorepo/docs folder
• Version branches as follows:
  • 2.x as the latest stable (default branch)
  • master as upcoming or development version
  • 1.x as legacy
• Ensure documentation updates are versioned correctly and pushed alongside framework releases.
• Needs in the readme to be clear this is a readonly reference repo, contributions are still in the monorepo

This matches how Laravel handles documentation branches and will make it easier to support automated tooling, enable version targeting, and allow downloading specific versions of the documentation without downloading unnecessary things.