load scale and offset if present

This Merge request adds the functionality to automatically load the scale and offset values from the input datasets into the STAC Metadata directly without having the user enter them manually, if present in the datasets.

However, if these values are not present or are incorrectly written in the data metadata, the user can use the write_scale_and_offset.py script to enter the values to the datasets and Raster2STAC should be able to read the correct values directly into the metadata afterwards.