README

Asana Task:
Dev cleanup: Use react-leaflet package
https://app.asana.com/0/1152340551558956/1153855588392657

It's mostly done and working
But tests are failing with "Map container not found"
See PaulLeCam/react-leaflet#246

I don't know how to fix that and need to move on to other tasks
so leaving this unfinished for now.