distribute as ECMAScript module (ESM)

[terencehonles]

I am using rollbar.js with Angular and by not providing an ESM distribution Angular complains this disables potential optimizations that ESM would allow. I am not sure if this is currently on the roadmap, but this is just a friendly request for this. I haven't looked at the code to see how much work this might be, but I figured I might as well make sure this was on the radar.

This is the specific warning and I am aware I can disable it https://angular.io/guide/build#configuring-commonjs-dependencies