Update README.md

[glenn-jocher]

copilot:all

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated and streamlined the Ultralytics documentation README for clarity and added multi-language support instructions.

📊 Key Changes

• Improved link to GitHub Actions workflow to show badge for gh-pages branch specifically.
• Simplified the installation instructions for the Ultralytics package in developer mode by merging lines for clarity.
• Cleaned up the section on building and serving locally, by combining lines and removing redundancy.
• Added a new section with detailed steps on how to build and serve documentation for multiple languages.
• Ensured that the deployment section succinctly covers key information on how to deploy the MkDocs site.

🎯 Purpose & Impact

• 📈 Enhanced readability by reducing clutter in installation and building instructions.
• 🌐 Multi-language support detail will assist developers in generating localized documentation, expanding the reach of Ultralytics documentation to non-English speaking users.
• 📝 Ensured developers can easily follow the steps to build, serve, and deploy their documentation in multiple languages, improving international accessibility and user experience.