PWA app to track the things I want to buy
You should have a firebase project dedicated to this app with a firestore database set up.
Then you have to include your own firebase app config object in order to use the application. I have approached this via firebase.config.js file (which is ignored by the way) and exporting the object. But you can do it your way.
I'm using vite for this project, the main scripts are included in package.json.