Included are the App.js file, the index.js file, and some other components (notably Button). A few things to take note of here:
You'll need to have your own Firebase app created and linked to your project. There's a variable in App.js named FIREBASE_URL which you need to set to your own Firebase app.
You'll also need to have created a Stripe account. Once you've made one, you can visit the Stripe site to get your API keys and copy-paste them in App.js and index.js, for the variables named SECRET_KEY and PUBLISHABLE_KEY.
You'll need to have Axios installed.