main
src: use `Utf8Value` and `TwoByteValue` instead of V8 helpers
src: use `Global` for storing resource in Node-API callback scope
src: initial enablement of IsolateGroups
src: fixup errorhandling more in various places
src: merge `CreateEnvironment()` overloads
src: fix winapi_strerror error string
src: keep global list of addon-provided cleanup hooks
src: cleanup unused headers