Can't use schema for json config

[Ismail Demirbilek]

Preflight checklist

• I could not find a solution in the existing issues, docs, nor discussions.
• I agree to follow this project's Code of Conduct.
• I have read and am following this repository's Contribution Guidelines.
• This issue affects my Ory Cloud project.
• I have joined the Ory Community Slack.
• I am signed up to the Ory Security Patch Newsletter.

Describe the bug

When using json config (instead of yaml) $schema property is not allowed.

Reproducing the bug

1. Create keto.json with contents:

{
  "$schema": "https://raw.githubusercontent.com/ory/keto/master/.schema/config.schema.json",
  "version": "v0.10.0",
  "log": {
    "level": "debug"
  },
  "namespaces": [],
  "dsn": "memory",
  "serve": {
    "read": {
      "host": "0.0.0.0",
      "port": 4466
    },
    "write": {
      "host": "0.0.0.0",
      "port": 4467
    }
  }
}

2. Run keto -c keto.json

Relevant log output

The configuration contains values or keys which are invalid:
  ^-- additionalProperties "$schema" not allowed

### Relevant configuration

_No response_

### Version

v0.10.0-alpha.1

### On which operating system are you observing this issue?

Linux

### In which environment are you deploying?

Docker Compose

### Additional Context

_No response_