docs: added type field in the documentation of package.json

[anuj123upadhyay]

Add documentation for package.json type field

What / Why

This PR adds comprehensive documentation for the type field in package.json, which was previously undocumented in the npm CLI documentation. The type field is an important Node.js feature that determines how .js files are interpreted (as ES modules or CommonJS modules) and was missing from the official npm package.json documentation.

Changes made:

• Added complete documentation for the type field between the exports and main sections
• Included practical JSON examples for both "module" and "commonjs" values
• Explained the behavior and implications of each type setting
• Added details about file extension handling (.js, .mjs, .cjs)
• Added reference to official Node.js documentation for additional details

This addition helps developers understand how to properly configure their packages for ES modules or CommonJS, which is crucial for modern Node.js development.

References

Fixes npm/cli#[8376] - Documents the missing type field in package.json

[ljharb]

i think rather than all of this content, it should be nothing more than a link to https://nodejs.org/api/packages.html#type, so that there's not two sources of truth to keep up to date.

[wraithgar]

This is generally the position we have also taken in other places in the docs. "nothing more" is a little extreme, some helpful copy explaining that the source of truth is found elsewhere would be appropriate.

[ljharb]

oh sure, that works fine :-) just, nothing technical, ie that would need to be updated in the future.