Actually, it kind of works now, my www must have been kind of stale. I installed the app-scripts as described here and webpack does its thing to miraculously include the JS from cal-heatmap in the apps main.js
Big question however - where are the source maps? I added: devtool: 'source-map', to the webpack.config.js but it doesn’t do anything - also, how to I add awesome-typescript loader etc?
Thanks.