message: [Improvement] add sideEffects config for webpack 4
diff: "packages",
  "types"
  ],
  + "sideEffects": [
  + "es/**/style/*",
  + "lib/**/style/*"
  + ],
  "scripts": {
  "bootstrap": "yarn || npm i && cd ./packages/vant-css/ && yarn || npm i && cd ../../",
  "dev": "npm run build:file && webpack-dev-server --inline --config build/webpack.config.dev.js",
  