Ability to update npmDependencies for Scala.js projects

[exoego]

It would be super-helpful for Scala.js users if Scala Steward update npmDependencies on scalajs-bundler plugin. npmDependencies is a setting key to define Node.js modules and its version, in a form of String -> String, like

npmDependencies ++= Seq(
  "aws-sdk" -> "2.743.0",
  "archiver" -> "5.0.0",
)

Suggestion for implementation (and comment for consideration)

1. Extract npm module names and versions
   • Maybe run show npmDependencies then parse the result ?
2. Fetch latest version of each npm modules
   • jsdelivr's /package/npm/:name API] could be used.
   • name -> latestVersion pairs should be cached, since external API invokations are costly.
3. Rewrite all occurence of name -> version to name -> latestVersion in *.sbt and project/*.(sbt|scala)
4. Creates a PR