Add KVM hertz model and make it compatible with numpy v2

[PinkShnack]

AFM-analysis/nanite#30

As discussed in a previous PR, it would be good to have the external Hertz KVM model in this repository.

• The KVM model currently exists here: https://data.mendeley.com/datasets/c2gccnfkgd/2

Todo

• The KVM model should have two versions, one (original from paper) for numpy v1 and one for numpy v2. Reason:
  • fit\_stop = int(np.argwhere(force < (max\_force * fraction_force))[0])\ fails for numpy v2

  • # numpy 1 and 2 compatible code
    _mask = force < (max_force * fraction_force)
    if not np.any(_mask):
        raise ValueError("No force values below threshold")
    fit_stop = int(np.argmax(_mask))

[PinkShnack]

closed with #5