Add Discord badge

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Added Discord badge to README and cosmetic changes to code documentation.

📊 Key Changes

• Added Discord community badge to the README for easier access to Ultralytics Discord.
• Re-formatted a block of code in export.py for better readability.
• In models/experimental.py and utils/loggers/__init__.py, inserted blank lines for consistency with the code convention.
• Minor documentation consistency adjustment in utils/loggers/clearml/clearml_utils.py.

🎯 Purpose & Impact

• 🤝 The new Discord badge on the README.md encourages community engagement by providing a quick link to join discussions and support channels.
• 📑 The code formatting changes improve the readability of the code, making it easier to understand and maintain.
• 🧹 The added blank lines and formatting tweaks demonstrate good coding practices and uphold the project's code quality standards.
• 🚀 No direct impact on functionality or performance; primary benefit is improving developer experience and community involvement.