Enhance documentation for STAC integration and Zarr asset access

[emmanuelmathot]

Update architecture and examples to clarify how STAC assets relate to Zarr stores, emphasizing direct access to Zarr groups and the importance of consolidated metadata. Include guidance on URL resolution and the role of the rel: store link.

Fixes #124

[m-mohr]

Maybe add @ahocevar to the reviewers as the OpenLayers GeoZarr source options were the initial starting point for the reverse parsing.

[ahocevar]

I added two comments to improve confusing parts of this documentation.

This is also to be seen in the context of openlayers/openlayers#17378, which suggests removing the group option of the OpenLayers GeoZarr source, in favor of providing a url that points to the multiscales root.

[ahocevar]

This is confusing, because s3://bucket/S2A_MSIL2A_20251008T100041.zarr/measurements/reflectance/r10m does not have consolidated metadata. I'd suggest changing to

Suggested change

	❌ s3://bucket/S2A_MSIL2A_20251008T100041.zarr/measurements.zarr/reflectance
	✅ s3://bucket/S2A_MSIL2A_20251008T100041.zarr/measurements/reflectance
	❌ s3://bucket/S2A_MSIL2A_20251008T100041.zarr/measurements.zarr/reflectance

[ahocevar]

This is confusing in the context of multiscales. Clients that support multiscales should receive asset urls with the available multiscales below them:

s3://bucket/S2A_MSIL2A_20251008T100041.zarr/measurements/reflectance