Fix detect.py URL inference

[glenn-jocher]

Allows detect.py to run inference on remote URL sources, i.e.:

!python detect.py --weights yolov5s.pt --source https://ultralytics.com/assets/zidane.jpg  # image URL
!python detect.py --weights yolov5s.pt --source https://ultralytics.com/assets/decelera_landscape.mov  # video URL

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced media source handling and format verification in the YOLOv5 detection script.

📊 Key Changes

• Added image and video format lists to detection utilities.
• Improved the clarity of the source type checking (webcam, file, or URL).
• Implemented automatic download of files from URLs if necessary.

🎯 Purpose & Impact

• 🎯 To streamline the process of identifying source types and handle them appropriately in the detection pipeline.
• 💡 Users benefit from more robust handling of various input source formats and the convenience of automatic file downloads when URLs are provided that point to valid media files.
• 🚀 Potential impact includes greater ease of use and a more user-friendly experience, especially for non-expert users not accustomed to manually downloading files for object detection tasks.