Not only `err`, `stats.hasErrors` also should be handled.
I found this bug in [Pipeline 42881 build] - some errors exist,
but build result was successful.

See also: https://webpack.js.org/api/node/#error-handling

[Pipeline 42881 build]: https://git.pleroma.social/pleroma/pleroma-fe/-/jobs/225066

https://stackoverflow.com/questions/69343038/cant-import-the-named-export-xxxx-from-non-ecmascript-module-only-default-expo

polyfills also.

generated properly

This reverts merge request !856