Add support for STAC catalogs

[nuest]

[Not sure this make much sense, revisit later...]

It might be the case at some point that a DOI points to a STAC collection or resource. Then it would be nice if the extent can be extracted. Makes more sense when remote data sources are supported.

geoextent -b -t https://url.to.stac/collection/1

See https://pystac.readthedocs.io/en/latest/quickstart.html#Reading-STAC for a Python lib.

Catalogs: https://stacindex.org/catalogs