Enhance description of `acalib.core.transform.fits_props`

[autopawn]

"""
Extracts properties information of the astronomical data cube.
Parameters
----------
img : numpy.ndarray
    Astronomical data cube.

Returns
-------
result : dict
    Dictionary with properties of the image: *centroid*, *major*, *minor*, *ratio*, *angle*, *area*, *img*, *clr*, *label*, *orig*.
"""

Doens't seem to be enough for this function that does a lot of things. Maybe describe each value of the output dictionary?