Natural Earth 1:110m Admin 0 country boundaries

Source:
https://github.com/nvkelso/natural-earth-vector/blob/master/geojson/ne_110m_admin_0_countries.geojson

Natural Earth data is in the public domain:
https://www.naturalearthdata.com/about/terms-of-use/

The bundled copy removes feature properties that are not needed by Contrail.
