Add interface for NEP potential

@JaGeo

Already ase interface exists for this potential in python packages along with training.
See for example :
PyNEP
calorine

So, it should be easy to add it to our workflow as well, without much effort on the coding side, I feel.

Authors have already shown applicability for harmonic phonons and MD simulations. I feel it could fit nicely in our package.

Also, I won't prioritize this as of now. It is not necessary to add it for the initial release.

I just wanted to add it as a note here so I don't forget it 😄

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