[feat] document on best practice of package.json for dual package (CJS+ESM)

[loynoir]

What is the problem this feature will solve?

I fork a typescript CJS repo to add ESM support.

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sinclairzx81/typebox#400 (comment)

Do you have any reference links on best practice to support both ESM and CJS? I assume the cjs and esm submodule pathing is a common, but curious on best practice configuration of package.json. I had been meaning to support ESM, however probably as a minor semver, as internal directories have been changed.

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I use below config, seems working, but not sure if it is best practice.

https://github.com/loynoir/typebox/blob/feat-esm/package.json#L13-L56

==> cjs/package.json <==
{"type":"commonjs"}

==> esm/package.json <==
{"type":"module"}

What is the feature you are proposing to solve the problem?

Official document on best practice of package.json for dual package (CJS+ESM).

What alternatives have you considered?

No response

[aduh95]

There's https://nodejs.org/api/packages.html#dual-commonjses-module-packages.

Closing for now, we can reopen if you think the docs is missing something (or don't hesitate to open a PR to improve the docs if you have suggestions).