Fetch topojson from magicbox-open-api and convert to geojson

[mikefab]

Task

Fetch topojson from magicbox-open-api and convert to geojson

Why do this

Currently only one admin level shapefile can be displayed in the app. It is hardcoded in ./routes/shapefile.js.

Since the app needs to feature more than one country, it should fetch shapefile data from an API. Since topojson cannot be used with leaflet, we need to convert it to geojson first.

[thoat]

This relates to unicef/magicbox-open-api#53.

[thoat]

However, in our recent discussions, we are considering to move from Leaflet to MapboxGL. Hence, we may or may not need to convert data to geojson.