update to STAC 1.0

[scottyhq]

I'm currently trying out the pystac 1.0rc1 release to update these small canned examples to STAC version 1.0 (stac-utils/pystac#441 (comment)).

I'm wondering if it would be ok to just store a few assets per item under the 100MB github limit and store directly in this repository? That way you guarantee the asset URLs work reliably, rather than using fake ones or ones that may change (such as the current landsat 8 example, which points to a bucket that will be deprecated on July1 (https://registry.opendata.aws/landsat-8/). Disadvantage of course is that the repo size will be big...