Update Discord invite link

[glenn-jocher]

@taliabender @sergiuwaxmann updates Discord links in HUB repo

copilot:all

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Update to Discord community links across repository documentation.

📊 Key Changes

• Updated Discord invitation links in various documentation files, including:
  • Main README.md file
  • Issue template configuration to guide users towards the new Discord link
  • README.md files within example dataset folders (coco8-pose, coco8-seg, and coco8)

🎯 Purpose & Impact

• 🎉 Ensures that users and contributors have access to the correct Ultralytics community channels.
• 🤝 Facilitates better support and community interaction by directing inquiries to the updated Discord server.
• 💡 Prevents confusion and improves user experience by providing consistent and up-to-date information across the repository.