Document how to add our data as a layer to your own map

[switzersc-usds]

Is your feature request related to a problem? Please describe. People are making new maps left and right with our data! Let's help them do it by documenting steps for the major map technologies so they don't have to reinvent the wheel each time.

Major map tech that it would be good to document for:

• Mapbox
• Open street maps
• ArcGIS

Note we have a shapefile available on the CEJST website as well as a vector tile API people can use (see #1754).

Describe the solution you'd like In the For Developers and Data Scientists section of our main README, I'd like to see a section for how to use CEJST data on my own map, with a link to a longer doc with the steps. I imagine there would be a section in the doc for each major map tech listed above, with the appropriate steps there for each.