experiment with babel-preset-env

[outofambit]

I'd like to explore using babel-preset-env to allow us to consistently support a range of browsers while using whatever ES features we'd like.

I'm not sure how this will impact the bundle size, so I'm going to look into that first.

(builds on #3431)

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There's a lot of other things we could have babel do, but I think the strongest case for babel in p5js is to ensure backward compatibility with older browser versions (or ones that are the minority in not supporting an ES syntax/feature) using babel-preset-env.

Supporting a range of browsers is much easier with babel-preset-env. When added to your build process, it will polyfill and transpile your javascript to work on the browser versions listed in a configuration file (which we maintain as part of our repo). It's super cool and would allow us to embrace whatever features of es6+ we find appropriate without limiting the library's (browser) reach.

Originally posted by @outofambit in #3425 (comment)