Update Discord invite URLs

[glenn-jocher]

copilot:all

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated Ultralytics Community Discord invite links across various documentation pages.

📊 Key Changes

• Discord invite links updated in .github/ISSUE_TEMPLATE/config.yml
• README.md and example datasets documentation (coco8-pose, coco8-seg, and coco8) Discord links updated.
• Update Discord link in hub.ipynb notebook.

🎯 Purpose & Impact

• Enhanced User Support: The updated Discord links ensure users have access to the current community support platform for help and discussions.
• Maintained Accessibility: Keeps the documentation and resources accurate and accessible for both new and existing community members.
• Community Engagement: Promotes active involvement in the Ultralytics community by directing users to the right place for real-time interactions with peers and developers.