napi: napi version doesn't been exposed through process.versions

[legendecas]

• Version: v8.11.1
• Platform: macos
• Subsystem: versions

NAPI version didn't been exposed through process.versions.

console.log(process.versions)
/*
{ http_parser: '2.8.0',
  node: '8.11.1',
  chakracore: '1.9.1.0',
  uv: '1.19.1',
  zlib: '1.2.11',
  ares: '1.10.1-DEV',
  modules: '57',
  nghttp2: '1.25.0',
  openssl: '1.0.2o',
  icu: '60.1',
  unicode: '10.0',
  cldr: '32.0',
  tz: '2017c' }
*/