Support Modern Browsers

I use nested Web Workers. This is not supported by all browser, see this. We can add a browserslist option to the package.js file.

./package.js

{
  "name": "ifc.js",
  "version": "1.0.1",
  "description": "IFC viewer",
  "main": "build/IFC.js",
  "module": "build/IFC.module.js",
  "browser": "build/IFC.min.js",
  "scripts": {...},
  "repository": {...},
  "keywords": [...],
  "author": "agviegas",
  "license": "MIT",
  "bugs": {...},
  "homepage": "https://github.com/agviegas/IFC.js#readme",
  "dependencies": {...},
  "browserslist":"last 2 Chrome versions"
}

This will tell Babel to only support the last 2 Chrome versions. Please note that this approach migh cause errors with other browser. That has to be tested!