Make Docker actions conditional on ultralytics/yolov5 repo

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced CI and Docker workflows for better repository management 🚀

📊 Key Changes

• Added new environment variable outputs to the CI testing workflow.
• Commented out the pull request trigger for Docker image publishing.
• Added a condition to only run the Docker job for the official Ultralytics repository.

🎯 Purpose & Impact

• 🛠 Improves debugging by echoing additional GitHub context variables in CI.
• 📝 Prevents unnecessary Docker builds on pull request events, conserving resources.
• 🛂 Ensures Docker images are only published from the main Ultralytics repository, protecting the integrity of official images and preventing accidental pushes from forks.

[glenn-jocher]

@Borda @AyushExel Docker builds no longer run on forks, thanks for the tip! The action still runs but shows as 'check skipped':

Verified on my personal fork at https://github.com/glenn-jocher/yolov5: