Include Ionic contribution of dielectric tensor

from a vibrational data, use the run_complex_dielectric_function function, and use as input for freq_range an array like np.array([0]). (note: it will return an array of shape (3,3,1)). this way the function will return the “full” static dielectric tensor. if you want the ionic cotribution only (indeed, given by born charges times phonon eigenmodes), subtract the dielectric tensor