Does not work with emojis in headers

[gaborbernat]

Here's the example, neither anchor generation or without is generating the proper HTML anchors.

Thank you for your interest in contributing! Please follow these guidelines to help us review and accept your changes
smoothly.

## 📬 Contact

For questions or support, open an issue or contact the maintainers listed in the [`CODEOWNERS`](CODEOWNERS) file.

## 🚀 Getting Started

1. ✨ **Fork the repository** and clone your fork locally.


## 🛠️ Development

- 📝 Follow the project's style and conventions.

## 🔀 Pull Requests

- 📬 Open pull requests against the `main` branch.

### 🗒️ Commit Messages

- 🏷️ Write clear, descriptive commit messages.

### 🚀 Release

- 🚦 Releases are triggered automatically when changes are merged into the `main` branch.

## 🤝 Code of Conduct

🙏 Be respectful and constructive in all interactions.

[kdeldycke]

Seems related to: hukkin/mdformat#312 (comment)