Add AAS facilities keywords to site-data?

### Description

It might be neat to add the AAS facilities keywords to our `sites.json`. If I looked up a site in astropy, I would know how to add the correct facility to my article. I can envision further uses where `sites.json` could be used to add keywords to data downloaded through astroquery, but those are beyond the scope of this repro. If the data is here, others may find other uses.

While I got this idea from looking at the list of AAS keywords, we should add a more generic category to the database, e.g. `{'journal keywords': {'AAS': keyword}}` to make it extensible if we add others later. The AAS journals are the only ones with a system like that right now that I'm aware of, though.

### Additional context

AAS journals facilities keywords: https://journals.aas.org/facility-keywords/
Maybe this could be done in collaboration with the AAS data editors? @augustfly

Inspect sites.json and the AAS facility-keywords page first. Add the facilities under an extensible journal-keywords/AAS structure, then verify that the JSON remains valid and the site records expose the intended keywords.

Written by the indexing model from the issue text.