feat(ion-modal): break point class & values

### Prerequisites

- [x] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#creating-an-issue).
- [x] I agree to follow the [Code of Conduct](https://ionicframework.com/code-of-conduct).
- [x] I have searched for [existing issues](https://github.com/ionic-team/ionic-framework/issues) that already include this feature request, without success.

### Describe the Feature Request

Add the breakpoint as a class name of the ion-modal.

### Describe the Use Case

As my app use border-radius, I had to apply the same to the modal _to keep it consistent_.

But when the modal it at the `1` breakpoint, I would like to remove the border-radius.

### Describe Preferred Solution

having a `breakpoint-[value]` class name, which will contain the value of the different possible breakpoint

### Describe Alternatives

Also possible to have only if the `ion-modal` is actually overflowing or not

```
nativeElement.scrollHeight > nativeElement.clientHeight
```

### Related Code

I could propose a PR if wished

### Additional Information

_No response_

Start by locating the ion-modal component and its breakpoint handling. Review how breakpoint values are represented and how modal classes are assigned. Done means the modal exposes a breakpoint-[value] class that reflects the active breakpoint and supports styling such as changing border-radius.

索引モデルが issue の本文から書いたものです。