I wonder how hard it would be to add basemap support to <a href="https:&#x2F;&#x2F;plot.ly&#x2F;javascript&#x2F;choropleth-maps&#x2F;" rel="nofollow">https:&#x2F;&#x2F;plot.ly&#x2F;javascript&#x2F;choropleth-maps&#x2F;</a>, a-la Leaflet.js.