feat: add ESM support

[dangreen]

Alternative of #10479

More changes than expected, but still.

To import CommonJS modules in/from ESM project .cjs extension is required.

[dangreen]

I think this PR also resolves this issue #9436

If we still want to support commonjs, cjs bundle from this PR has compatible with ESM exports:

Chart.helpers = {...helpers};
Chart._adapters = _adapters;
Chart.Animation = Animation;
Chart.Animations = Animations;
Chart.animator = animator;
Chart.controllers = registry.controllers.items;
Chart.DatasetController = DatasetController;
Chart.Element = Element;
Chart.elements = elements;
Chart.Interaction = Interaction;
Chart.layouts = layouts;
Chart.platforms = platforms;
Chart.Scale = Scale;
Chart.Ticks = Ticks;
Object.assign(Chart, controllers, scales, elements, plugins, platforms);
Chart.Chart = Chart;
module.exports = Chart;

@benmccann What do you think?

[benmccann]

I'd love to drop CJS and do ESM-only if possible

[kurkle]

I'm not sure how the files should be named, because I guess chart.js can't be UMD when type='module'.

[kurkle]

Just one more comment (considering all of the package.json's)

[kurkle]

Needs a rebase though

[kurkle]

Something about this should be mentioned in https://www.chartjs.org/docs/master/migration/v4-migration.html but I don't want to hold because of that.

[dangreen]

I will resolve conflicts later today

[benmccann]

Should we keep the unminified UMD build? It might help people if they encounter an error in the minified build or otherwise want to debug. Perhaps we should have a chart.umd.js and chart.umd.min.js?

[dangreen]

@benmccann maybe just emit sourcemaps for UMD bundle ?