The `useESModules` option is unnecessary only when the target bundlers
support exports conditions in `package.json`.

When they don't, it's not possible to force them to use the native ESM
files unless you use this option, that makes it work by using a different
non-overloaded entrypoint.

This makes sure that even if the target bundler doesn't support export
conditions in `package.json`, an ESM helper will only load other ESM
helpers.