Fix bug in make_nifti method to handle Path objects correctly

[mcsitter]

This pull request includes a bug fix in the pypet2bids/ecat.py file and I added myself to the contributors.md file.

I modified the make_nifti method to correctly check if the output file name ends with "nii.gz" using pathlib.Path(output).name instead of checking the entire path string. Since pathlib.Path objects are not iterable, the "nii.gz" not in output check would otherwise throw a TypeError, if output is not a string but a Path object. Since providing the nifti_file as a pathlib.Path object does not throw errors in other places of the code, at least when running .convert(), I considered this a bug.

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📚 Documentation preview 📚: https://pet2bids--333.org.readthedocs.build/en/333/

[bendhouseart]

Nice catch, thanks! I went ahead and did some significant refactoring just now. I would ask that you re-sync your main branch and merge it into mcsitter:path-1. Will hit the squash and merge as soon as that's taken care of.

[bendhouseart]

Actually that shouldn't matter, it's two small changes. I'm going to send it.