improvements to ESM support, module library, import chunk loading, module externals

[sokra]

What kind of change does this PR introduce?
feature

Did you add tests for your changes?
yes

Does this PR introduce a breaking change?
no

What needs to be documented once your changes are merged?

• output.library.type: "module" is now experimentally supported
• output.chunkLoading: "import" uses import() to load chunks
• output.chunkFormat: "module" uses ESM exports to expose chunk data
• experiments.outputModule will now use output.chunkFormat: "module", output.chunkLoading: "import"
• externalsType: "module" generates now import * as X from "..." (in a module) or import("...") (in a script)
• externalsType: "node-commonjs" generates import { createRequire } from "module" when in a module
• externalsPresets use node-commonjs now when node.js related

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[alexander-akait]

Maybe we can read package.json here and use js when "type": "module" (same for filename)?

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[webpack-bot]

I've created an issue to document this in webpack/webpack.js.org.

[Jack-Works]

I cannot let my webpack 5.46 emit import(...) with this config. Is this feature released?

[Jack-Works]

Oh sorry I forgot to export config file