message: chore: clean up dist before build
diff: "scripts": {
  "test": "jest --coverage",
  "clean": "del dist coverage examples/build",
  + "clean:build": "del dist",
  "lint": "run-p lint:js lint:ts",
  "lint:js": "eslint .",
  "lint:ts": "tslint 'src/**/*.ts?(x)'",
  - "build": "run-s build:es build:cjs build:umd build:umd:min",
  + "build": "run-s clean:build build:es build:cjs build:umd build:umd:min",
  "build:es": "cross-env NODE_ENV=es rollup -c",
  "build:cjs": "cross-env NODE_ENV=cjs rollup -c",
  "build:umd": "rollup -c",
  