message: app: use app:serve and remove react-scripts dependency
diff: "react": "^16.12.0",
  "react-dom": "^16.12.0",
  "react-router-dom": "^5.1.2",
  - "react-scripts": "^3.4.0",
  "react-use": "^13.24.0",
  "zen-observable": "^0.8.15"
  },
  "scripts": {
  - "start": "cross-env EXTEND_ESLINT=true SKIP_PREFLIGHT_CHECK=true backstage-cli watch-deps -- react-scripts start",
  + "start": "backstage-cli app:serve",
  "build": "backstage-cli app:build",
  "test": "backstage-cli test",
  "lint": "backstage-cli lint"
  