Add get_coco128.sh for downloading the coco128 dataset

[zldrobit]

Add a script get_coco128.sh for downloading the coco128 dataset, which accelerates training validation and testing.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Introducing a simple script for easy downloading of the COCO128 dataset.

📊 Key Changes

• New get_coco128.sh bash script added to automate dataset download and setup.
• Allows quick downloading and setup of the COCO128 dataset for training with just one command.

🎯 Purpose & Impact

• 🎯 Simplifies the process of obtaining the COCO128 dataset, making it more user-friendly for both beginners and advanced users.
• 🚀 Can accelerate the setup time for training YOLOv5 models, as it provides a quick way to access a small, yet useful dataset.
• 👩‍💻 Benefits users looking to experiment with or prototype object detection models without requiring the full COCO dataset's size and complexity.

[glenn-jocher]

@zldrobit thank you for your contributions!

I'm guessing this makes calibrating the TFLite quantization a little easier?

[zldrobit]

@glenn-jocher Yes, you're right.
With this script, it will be more convenient to calibrate the TFLite quantization model and do testing on google Colab.