Add an `editorconfig-checker-fix` pre-commit hook

## Proposal

Add a dedicated `editorconfig-checker-fix` hook to `.pre-commit-hooks.yaml` that runs `editorconfig-checker --fix`, once this wrapper targets an upstream release containing the `--fix` mode from editorconfig-checker/editorconfig-checker#612.

The existing `editorconfig-checker` hook should remain check-only. A separate hook would expose the upstream opt-in fixing mode directly through pre-commit without requiring users to add `args: [--fix]` themselves.

## Usage

```yaml
repos:
- repo: https://github.com/editorconfig-checker/editorconfig-checker.python
hooks:
- id: editorconfig-checker-fix
```

## References

- Upstream `--fix` implementation: editorconfig-checker/editorconfig-checker#612
- https://github.com/editorconfig-checker/editorconfig-checker.python/blob/main/.pre-commit-hooks.yaml
- https://github.com/editorconfig-checker/editorconfig-checker.python/blob/main/README.md

Start with .pre-commit-hooks.yaml and confirm the wrapper targets an upstream editorconfig-checker release containing the --fix mode from issue #612. Compare the existing hook configuration and the referenced README usage. Done means a separate editorconfig-checker-fix hook runs editorconfig-checker --fix while the existing hook remains check-only.

Written by the indexing model from the issue text.