feat: public accessable ionic.config.json Schema file

### Prequisites

- [X] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/.github/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

I would like to add a $schema to my ionic.config.json in case when I forgot what options are possible. Angular for example does have that as well for their angular.json its public but they force the node_modules installed schema file. I would like to have that for ionic (and Capacitor) too.

### Describe the Use Case

Forgetting options, validation, help

### Describe Preferred Solution

- Public CDN url
- node_modules/@ionic/core/ionic.config.schema.json e.g.

### Describe Alternatives

VS Code extension that provide it out of the box

### Related Code

_No response_

### Additional Information

_No response_