Ingest xshyne spectra

[lesliech1004]

Create the fits files and ingest the spectra for the XSHYNE library of Xshooter spectra

Link to relevant issue: Closes #468

For data ingests:
[ ] includes script used for ingest
[ ] includes modified JSON files
[ ] Add new tests
[ ] Update the Versions table

[kelle]

FITS files:

• experiment with adding a mask for data < 0.6 microns and in the noisy "in-between" regions.
• add more SPECBAND header keywords
• Find TMID and add COMMENT to FITS files about multiple observation dates.

Ingest:

• ingest each file twice, once for "optical" and once for "nir".
• Use earliest date for SIMPLE observation_date. add comment to SIMPLE entry "Multiple observation dates."

[lesliech1004]

meant mask 0.2-0.6μm wavelength values

[kelle]

This is looking really good! The mask function is excellent.

• please take the code from the notebook and turn it into a script (.py file) to convert the spectra and make new FITS files with the mask.

converted_spectrum = Spectrum(
        spectral_axis=wave * u.um,
        flux=flux * u.Jy,
        uncertainty=StdDevUncertainty(err * u.Jy)
        mask = mask
    )
    ```
- Modify the notebook to read in those new FITS files and plot them.