static-web-apps-cli/docs/swa-cli.config.json

{
  "$schema": "https://aka.ms/azure/static-web-apps-cli/schema",
  "configurations": {
    "docs": {
      "appLocation": "www",
      "outputLocation": "build",
      "appBuildCommand": "npm run build",
      "run": "npm start",
      "devServerUrl": "http://localhost:3000"
    }
  }
}