bug: The default firestore.json file generates an array of functions#196

### Describe the Bug Firebase 11.19.0 (dec/2022): running `firebase init` with functions setup generates the following snippet: ```json "functions": [ { "source": "functions", "codebase": "default", "ignore": ["node_modules", ".git", "firebase-debug.log", "firebase-debug.*.log"] } ], ... ``` which is an array. The adapter expects an object. ### Steps to Reproduce 1. run `firebase init` and make sure you selected to setup firebase functions 3. run `npm run build` 4. The following error will throw: `Error: Required "functions.source" field is missing from Firebase Configuration file.` ### Expected Behaviour The adapter should accept this default configuration. Probably this will be the default to now on. ### svelte-adapter-firebase version 0.14.4 ### sveltejs/kit version 1.0.1