message: Add clean script, pin typescript to major version
diff: "test": "echo \"Error: no test specified\" && exit 1",
  "build": "tsc",
  "fmt": "prettier --write 'src/**/*.ts'",
  - "check-fmt": "prettier --check 'src/**/*.ts'"
  + "check-fmt": "prettier --check 'src/**/*.ts'",
  + "clean": "rm -r ./dist"
  },
  "author": "",
  "license": "Apache-2.0",
  "husky": "^1.3.1",
  "lint-staged": "^8.1.5",
  "prettier": "^1.16.4",
  - "typescript": "~3.4.0"
  + "typescript": "^3.4.0"
  },
  "husky": {
  "hooks": {
  