message: Add webextension polyfill
diff: "useragent": "^2.3.0",
  "validator": "*",
  "waypoints": "^4.0.1",
  + "webextension-polyfill": "^0.4.0",
  "webpack-hot-middleware": "^2.21.0",
  "withinviewport": "^1.0.0",
  "xss": "^0.3.4"
  