Implement STAC endpoint for Stanford (+ Public Domain?) data items

[thatbudakguy]

Makes EW content natively accessible through code.

i.e. https://raw.githubusercontent.com/samapriya/awesome-gee-community-datasets/master/catalog/stac_catalog.json

For programmatic access ala:
https://pystac.readthedocs.io/en/stable/

https://cran.r-project.org/web/packages/rstac/readme/README.html

(This is another step towards a day when we can auto-archive Planet.com assets used by Stanford researchers, then serve them internally through stac)

[thatbudakguy]

this might be something we do at the level of OpenGeoMetadata or entirely external to Earthworks.