Summary

Since versions 1.11.0/2.1.0, jQuery has used a module wrapper with one strange
addition - in CommonJS environments, if a global window with a document was
not present, jQuery exported a factory accepting a window implementation and
returning jQuery.

This approach created a number of problems:

1. Properly typing jQuery would be a nightmare as the exported value depends on
   the environment. In practice, typing definitions ignored the factory case.
2. Since we now use named exports for the jQuery module version, it felt weird
   to have jQuery and $ pointing to the factory instead of real jQuery.

Instead, for jQuery 4.0 we leverage the just added exports field in
package.json to expose completely separate factory entry points: one for the
full build, one for the slim one.

Exports definitions for ./factory & ./factory-slim are simpler than for .
and ./slim - this is because it's a new entry point, we only expose a named
export and so there's no issue with just pointing Node.js to the CommonJS
version (we cannot use the module version for import from Node.js to avoid
double package hazard). The factory entry points are also not meant for the Web
browser which always has a proper window - and they'd be unfit for an
inclusion in a regular script tag anyway. Because of that, we also don't
generate minified versions of these entry points.

The factory files are not pushed to the CDN since they are mostly aimed
at Node.js.

Checklist

• New tests have been added to show the fix or feature works
• If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com