Formats a date according to the document language: a German long date
(e.g. `1. Januar 2024`) for German, otherwise an English long date.
Arguments
- date
A `Date` (or object coercible by [format()]).
- lang
Language code. Defaults to the document's `lang` metadata field,
falling back to `"de_CH"`. German is used for `"german"`, `"de-DE"` and
`"de-CH"`; any other value yields the English format.
Value
A formatted date string.