Add facebook collection and item to staging API

[abarciauskas-bgse]

Data set exists in testing API: https://j2wlly6xg8.execute-api.us-east-1.amazonaws.com/collections/facebook_population_density

@slesaad was working on automating the COG generation in this ticket NASA-IMPACT/veda-data#78

This ticket is just to publish the existing COG collection and item STAC metadata to the staging API, following NASA-IMPACT/veda-backend#29 and NASA-IMPACT/veda-backend#28

[slesaad]

Added the stac medata for the collection and item to the staging api. You can find it in the following links:
Collection: https://staging-stac.delta-backend.xyz/collections/facebook_population_density
Item: https://staging-stac.delta-backend.xyz/collections/facebook_population_density/items

cc: @abarciauskas-bgse @anayeaye

[abarciauskas-bgse]

LGTM @anayeaye do you want to take a look?

[anayeaye]

I forgot to comment, but did look at these a while back and they look good to me, too