`amplify init --app` flow should error if repo does not contain an `amplify/` directory

### Is this feature request related to a new or existing Amplify category?

_No response_

### Is this related to another service?

_No response_

### Describe the feature you'd like to request

When using [`amplify init --app `](https://docs.amplify.aws/cli/start/workflows/#clone-sample-amplify-project), the CLI should error if it is unable to detect an `amplify/` directory in the project root. This mitigates the (potentially) unintentional creation of an new, empty project.

### Describe the solution you'd like

```
amplify init --app git@github.com:josefaidt/not-an-amplify-project.git
🛑 The repository josefaidt/not-an-amplify-project does not contain an `amplify/` directory
```

### Describe alternatives you've considered

n/a

### Additional context

_No response_

### Is this something that you'd be interested in working on?

- [ ] 👋 I may be able to implement this feature request

### Would this feature include a breaking change?

- [ ] ⚠️ This feature might incur a breaking change