Move datasource from Google Apps Script to Webapp

[eugenethreat]

The Google Apps Script is not as performant as I would like it to be - map load time has increased from ~2 seconds (fetching geojson files from this repo) to ~5 seconds (fetching geojson from Google Apps Script). It may be worth seeing if writing an actual webapp to generate the geojson instead of using Google Apps Script is more performant.

Apps Script also has limited access control - in order for the GH Pages site to access the generated geojson, it's currently queryable by anyone. Functionally, this is the same as the old approach of having the geojson files in a public repo, but with a webapp we could enforce only accepting requests from the GH pages site VS anyone.

This would require spinning up another app on a PaaS such as Heroku or Render.