Adding a CoreML Export Script to Enhance Community Resources

[malfihasan]

I have been working on a CoreML project as a personal endeavor. I believe it could be beneficial to the community, so I am adding a coreml_export.py script for everyone's use. The script is added to tools/coreml_export.py.

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[mbotsu]

Hi.

Thanks to PR I was able to convert to CoreML. When I ran it, I found a bug in the code and unnecessary arguments and imports.

As an additional request, I think it would be even better if the device defaults to CPU and optionally GPU.