- **WebAppUser Class Fields**: Added missing `is_premium`, `added_to_attachment_menu`, and `allows_write_to_pm` fields to `WebAppUser` class to align with the Telegram API.

- **WebAppChat Class Implementation**: Introduced the `WebAppChat` class with all its fields (`id`, `type`, `title`, `username`, and `photo_url`) as specified in the Telegram API, which was previously missing from the library.

- **WebAppInitData Class Fields**: Included previously omitted fields in the `WebAppInitData` class: `chat`, `chat_type`, `chat_instance`, to match the official documentation for a complete Telegram Web Apps support.
