Package command - add support for multi modules

[lwronski]

No description provided.

[alexarchambault]

Apart from the minor comment, LGTM!

[romanowski]

Shouldn't we update js documentation?

[armanbilge]

This feature is already mentioned in the documentation, it just wasn't working :)

https://scala-cli.virtuslab.org/docs/reference/cli-options/#--js-module-split-style

[lwronski]

Shouldn't we update js documentation?

I think, that I confusingly named PR, it is more bug fixes. Because if someone run package --js command with the following scala file:

  @JSExportTopLevel(name = "onRequest", moduleID = "request_type")
  def func(...)

  @JSExportTopLevel(name = "onRequest", moduleID = "request_headers")
  def func(...)

he gets an error that main class is missing, when run generated js file. This PR fixed it.

[romanowski]

That is valid, however current Scala JS guide does not have a section about publishing so I think we should describe the publishing for JS. We have a small section at publish command but I think it only covers a basic scenario.

So I am merging this PR for now, @lwronski could you review the documentation for packaging in JS and create a follow up PR if needed?

[armanbilge]

Note that publishing (i.e., uploading SJSIR files to Maven) is different from packaging (linking SJSIR files into JS files).