gatsby-react-app
$ npm i -g gatsby-cli
# or
$ sudo npm i -g gatsby-cli
$ gatsby new gatsby-demo-app
$ cd gatsby-demo-app && gatsby develop
# auto open browser on `http://localhost:8000`
$ gatsby build
$ gatsby serve
$ gatsby -h
# or
$ gatsby --help
# gatsby COMMAND_NAME --help
$ gatsby new --help
$ open http://localhost:8000/
$ open http://localhost:8000/___graphql
# or
$ open http://localhost:8000/ && open http://localhost:8000/___graphql