Bundle for npm build

[bkazi]

The code uses JavaScript that needs to be transpiled and optimised for good browser support and load times
Best not to leave this to library users, especially since they might not want to transpile the way we expect.
What module bundler should be used? (stick with Webpack? or use Rollup, etc.)

[bkazi]

Uses webpack for UMD bundling and typescript compiler to transpile to commonjs and es modules (both unbundled)