babel-preset-env: `DEBUG` option

Using targets:
{
  "chrome": "60"
}

Using modules transform: commonjs

Using plugins:
  transform-async-generator-functions { "chrome":"60" }
  syntax-object-rest-spread { "chrome":"60" }
  transform-optional-catch-binding { "chrome":"60" }
  transform-unicode-property-regex { "chrome":"60" }

Using polyfills with `entry` option:

[src/in.js] Replaced `babel-polyfill` with the following polyfills:
  es7.promise.finally { "chrome":"60" }
  web.timers { "chrome":"60" }
  web.immediate { "chrome":"60" }
  web.dom.iterable { "chrome":"60" }
src/in.js -> lib/in.js