Kotlin JS GitHub Action SDK

Kotlin JS utilities for writing GitHub Actions, including wrappers for actions/toolkit packages, except for @actions/github and @actions/tool-cache. @actions/tool-cache will be added once blocking dukat bugs are fixes.

In addition to the @actions bindings, a utility Path class modeled after Python's pathlib is included, as are some miscellaneous utilities (like JsObject and an OS enum and detector).