{
  "private": true,
  "dependencies": {
    "@arcgis/core": "^4.18.1"
  },
  "devDependencies": {
    "@rollup/plugin-commonjs": "^15.0.0",
    "@rollup/plugin-node-resolve": "^9.0.0",
    "ncp": "^2.0.0",
    "npm-run-all": "^4.1.5",
    "rollup": "^2.26.11",
    "rollup-plugin-delete": "^2.0.0",
    "rollup-plugin-terser": "^7.0.2",
    "serve": "^11.3.2"
  },
  "scripts": {
    "build": "rollup -c",
    "copy": "ncp ./node_modules/@arcgis/core/assets ./public/assets",
    "watch": "rollup -c -w",
    "dev": "npm-run-all --parallel start watch",
    "start": "serve public",
    "postinstall": "npm run copy"
  }
}

{
  "private": true,
  "dependencies": {
    "@arcgis/core": "^4.18.1"
  },
  "devDependencies": {
    "@rollup/plugin-commonjs": "^15.0.0",
    "@rollup/plugin-node-resolve": "^9.0.0",
    "ncp": "^2.0.0",
    "npm-run-all": "^4.1.5",
    "rollup": "^2.26.11",
    "rollup-plugin-delete": "^2.0.0",
    "rollup-plugin-terser": "^7.0.2",
    "serve": "^11.3.2"
  },
  "scripts": {
    "build": "npm run copy && rollup -c",
    "copy": "ncp ./node_modules/@arcgis/core/assets ./public/assets",
    "watch": "npm run copy && rollup -c -w",
    "dev": "npm-run-all --parallel start watch",
    "start": "serve public",
    "postinstall": "npm run copy"
  }
}

Add asset copy commands to build and watch.
Add asset copy commands to build and watch.
