sp-dev-fx-webparts/samples/react-themes/config/package-solution.json

{
  "solution": {
    "name": "react-themes-client-side-solution",
    "id": "46489282-ffa9-4f00-939c-6fff916b182f",
    "version": "1.0.0.0"
  },
  "paths": {
    "zippedPackage": "solution/react-themes.sppkg"
  }
}