Load modern ES bundle in modern browsers

It seems to be becoming fairly common practice to generate two versions of an application’s JavaScript bundle: one that retains most of the features and syntax of modern JavaScript, and a second that compiles down to pure ES5 for maximum compatibility. There’s a slightly hacky but ultimately quite simple way to make sure the right bundle flavor is loaded, by using <script type="module"> and nomodule respectively.

We should explore setting things up this way in Popcode. I think it would mostly be worth the extra complexity if the modern JS bundle were substantially smaller than the legacy bundle, so worth investigating that first.

Start by reviewing the issue and the linked module/nomodule reference, then inspect how Popcode currently produces and loads its JavaScript bundles. Compare the sizes and browser compatibility of modern and ES5 output; the work is complete when the benefit is established and a concrete implementation path is documented or adopted.