message: package: clean dist-firefox.zip after build
diff: "pack:chrome": "node tools/pack.js",
  "pack:firefox": "web-ext build -s dist -a artifacts",
  "release": "npm run build:chrome:prod && npm run pack:chrome && npm run build:firefox:prod && npm run pack:firefox",
  - "release:firefox": "npm run build:firefox:prod && npm run pack:firefox",
  + "release:firefox": "npm run build:firefox:prod && npm run pack:firefox && rimraf artifacts/dist-firefox.zip",
  "release:chrome": "npm run build:chrome:prod && npm run pack:chrome",
  "test": "gulp lint && npm run release"
  },
  