See it deployed here: https://pacific-retreat-29989.herokuapp.com/.
The src/ folder contains two folders: client/ and server/. The client is a React app and the server an Express server, which uses MongoDB as a data store.
You will need to cp sample.env .env to your own .env file to store your environment variables, and fill in the values with your own tokens for MongoDB and GitHub.
To build the project code, run npm run build. This will build the client and server code to directory dist/.
From here, the app should be deployable to services like Heroku. Running npm start can be used to start the production app, using the entry file: dist/server/index.js.