message: build(root): remove spec.js + spec.d.ts files from build artifacts
diff: "scripts": {
  "postinstall": "yarn clean && yarn build && sleep 5s && yarn test",
  "build": "lerna run build",
  + "postbuild": "rimraf packages/**/*.spec.js packages/**/*.spec.d.ts",
  "benchmark": "make -C benchmarks",
  "watch": "lerna run --parallel --stream watch",
  "lint": "lerna run lint",
  