Minor change to the Readme for Firebase Console project name

I'm REALLY glad this was redone so I can start to get a handle on some best practices when using Firestore database ... prior to the real course getting done. I can at least contribute by helping to find documentation changes and minor bug fixes.

Minor fix for anyone to perform or for Andrea to make minor change in the Readme:

**Andrea could change the Readme:** In the readme it says: `Create a new project with the Firebase console` but it should probably say `Create a new project with the Firebase console with the name starter-architecture-flutter`.

**Users:** When creating the project in in the Firebase Console. either
- use the project name: `starter-architecture-flutter` or
- change the `.firebaserc` in the app to the name you chose in the Firebase Console or
- just delete `.firebaserc` and flutterfire will ask you which project to use when you run `flutterfire config`

```
{
"projects": {
"default": "my-project-name-in-lower-case"
}
}
```

Start with the README instructions for creating a project in the Firebase Console and compare them with the `.firebaserc` example in the issue. Update the project-name guidance, then verify that the documented alternatives for `.firebaserc` and `flutterfire config` are accurate and complete.

Written by the indexing model from the issue text.