add STAC raster extension to Sentinel 2 items

[mhungen]

Please consider adding the STAC raster extension to your Sentinel-2 catalogs.

This would make it much easier to process data using tools like odc.stac.
Currently, users have to rely on workarounds like this one. While not a major issue, it can be frustrating—especially when working with RGB images.

Additionally, this change would allow odc.stac to automatically select the most appropriate data type for an array (e.g., uint16 instead of defaulting to float32).

It would also enable the inclusion of BOA (scale/offset) information at the asset level, which is often overlooked. Many calculations may be slightly inaccurate because users forget to apply these corrections:
#349
#134

[777arc]

Great suggestion, we will look into this!