Default module kind to NoModule in ScalaJs

This better aligns with the defaults users coming from sbt land or going
to sbt where Scalajs will default to NoModule. This also allows a JS
file produced by package to more easily be incuded in an html file if no
further linking is required.

Closes VirtusLab#338

modules/build/src/main/scala/scala/build/options/ScalaJsOptions.scala

@@ -34,7 +34,7 @@ final case class ScalaJsOptions(
       case "commonjs" | "common" => ModuleKind.CommonJSModule
       case "esmodule" | "es"     => ModuleKind.ESModule
       case "nomodule" | "none"   => ModuleKind.NoModule
-      case _                     => ModuleKind.CommonJSModule
+      case _                     => ModuleKind.NoModule
     }
 
   def finalVersion = version.map(_.trim).filter(_.nonEmpty).getOrElse(Constants.scalaJsVersion)