Add support for `SmallModulesFor(packages)` Scala.js split-style

[armanbilge]

This is an important feature for efficiently integrating with bundlers.

https://www.scala-js.org/news/2022/04/04/announcing-scalajs-1.10.0/#new-module-split-style-smallmodulesforpackages

• Fix #4327: SmallModulesFor module split style scala-js/scala-js#4658

Thanks!