Full transition to ES modules

[birdofpreyru]

Right now Webpack builds the web-bundle of the library into CJS modules, with imports effectively replaced by require, which now causes issues with libraries like react-router (see remix-run/react-router#12770), which expose different builds for import and require entries from the host code. So... we should transition to building everything into MJS.

[birdofpreyru]

Well... it is tricky, due to different level of ES modules support in different tools we depend upon, let's hold it for now.

[birdofpreyru]

On the other hand, as js-utils already published as ES-modules built, we probably need to pull this through, or revert js-utils changes.

[birdofpreyru]

js-utils re-published as the dual CJS/MJS lib, will put this one on hold.

[birdofpreyru]

Also webpack.weakRequire() implementation relies on require() now... will it work with full ESM modules?