Add ES-browser build

[TimvdLippe]

This build is intended for users who want to use Redux in a browser with ES modules support. The build removes all references to process by assuming it is in a production environment.

Additionally, it does not transpile, as all browsers that have ES modules support also support ES2015+

This approach is similar to the one of Vue (vuejs/vue#7110) which I have also been using with success.

Fixes #2907

[timdorr]

Hey Tim, it's Tim 😄

I'm wondering if we can keep this in the es path, but output redux.browser.js or something like that.

What happens with symbol-observable in this bundle?

[TimvdLippe]

Hey! Yes that should be possible. Let me take a look on how to configure rollup for that.

Because ES modules are scoped, symbol-observable is bundled in. While this is a very small performance penalty (in the scenario that you would use symbol-observable somewhere as well), the package is so small I doubt it is relevant.

[TimvdLippe]

@timdorr Updated, PTAL 😄

[timdorr]

I'm actually mucking about with the babel and rollup configs right now. I'll have a conflict ready for you in just a second...

[TimvdLippe]

@timdorr Conflict should be busted 🎉

[TimvdLippe]

Hm, let me actually minify just like the minified umd build.

[timdorr]

Cool. I renamed it to just redux.mjs for simplicity. Forgot about that extension.

[TimvdLippe]

Thanks for the quick review @timdorr ! Can't wait for the next release 🎉

[TimvdLippe]

@timdorr What is the ETA of a release of a new version of Redux which includes this PR?

[Andarist]

According to ES modules support taken from here - https://github.com/babel/babel/blob/6b8261bbb7ebb8d2980cb30c3b3369678fd99835/packages/babel-preset-env/data/built-in-modules.json#L1-L11 and testing only desktop browsers quickly it seems that used object rest spread syntax in the es/redux.mjs is not supported in those verstions of Edge & Safari.

Depending on what the audience of this bundle is it might need to get adjusted.