Update export.py docstring

[glenn-jocher]

Format	Example	Export include=(...) argument
PyTorch	yolov5s.pt	-
TorchScript	yolov5s.torchscript.pt	'torchscript'
ONNX	yolov5s.onnx	'onnx'
CoreML	yolov5s.mlmodel	'coreml'
TensorFlow SavedModel	yolov5s_saved_model/	'saved_model'
TensorFlow GraphDef	yolov5s.pb	'pb'
TensorFlow Lite	yolov5s.tflite	'tflite'
TensorFlow.js	yolov5s_web_model/	'tfjs'

🛠️ PR Summary

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🌟 Summary

Enhanced support for exporting YOLOv5 models to various formats.

📊 Key Changes

• 👩‍💻 Added a clearer table showing support for different export formats.
• 🧰 New export format list includes PyTorch, TorchScript, ONNX, CoreML, and various TensorFlow options.
• 🔄 Updated usage instructions for consistency with the new export capabilities.
• 🌐 Included inference usage, demonstrating how newly exported formats can be used.

🎯 Purpose & Impact

• 📈 Aims to provide users with better documentation on how to export models to different formats, making it more accessible.
• 🚀 Enables wider deployment of YOLOv5 models across various platforms and devices by simplifying the export process.
• 👌 Improved user experience for those looking to integrate YOLOv5 into different production environments with clear guidance on usage.