message: [improvement] add sideEffects to enable tree shaking
diff: "webpack-cli": "^3.3.2",
  "webpack-dev-server": "3.3.1"
  },
  + "sideEffects": [
  + "es/**/style/*",
  + "lib/**/style/*",
  + "*.css",
  + "*.less"
  + ],
  "vetur": {
  "tags": "vetur/tags.json",
  "attributes": "vetur/attributes.json"
  