Add spiral variable-radii sinusoidal spiral crystals in tf.spectro.spectral_range_2d()

[dvezinet]

Implement variable-radii sinusoidal spiral crystals in tf.spectro.spectral_range_2d()

[1] N. A. Pablant et al., “Design and expected performance of a variable-radii sinusoidal spiral x-ray spectrometer for the National Ignition Facility,” Review of Scientific Instruments, vol. 92, no. 9, p. 093904, Sep. 2021, doi: 10.1063/5.0054329.
[2] N. A. Pablant et al., “A new class of variable-radii diffraction optics for high-resolution x-ray spectroscopy at the National Ignition Facility (invited),” Review of Scientific Instruments, vol. 93, no. 10, p. 103548, Oct. 2022, doi: 10.1063/5.0101856.