Add Hungarian translation (hu) for Kifli.hu

[dvejsada]

Add a Hungarian translation (hu.json) for users of Kifli.hu.

Contributions are very welcome! 🙌 No coding is needed: it's one JSON file. Comment here if you'd like to take it, so nobody else starts the same translation.

Steps

1. Copy custom_components/rohlikcz/translations/en.json to custom_components/rohlikcz/translations/hu.json.
2. Translate the text values only. Keep the keys and placeholders such as {name} unchanged.
3. Where it makes sense, use the same terms as the Kifli.hu app (cart, delivery slot, credit and so on).
4. Open a pull request.

Part of #96.