US: add feeds for major metropolitan cities (Los Angeles, San Francisco, New York City, Boston, Washington, etc.)

[nekohayo]

Those are very populous cities, and also tend to be tourist attractions, so it might make sense to add them first? I suspect these cities all have open transit data. Looking at OpenMobilityData transit feeds for the USA, I can see:

• New York
• Los Angeles and surrounding suburbs and counties (as seen in the map and sidebar on the right) - the Los Angeles metropolitan area seems to be a big pile of counties in a trenchcoat, each with their own mini transit system
• Boston and Massachusetts
• San Francisco and the Bay Area Transit Authority
• Seattle
• others?