CsvConfig(parseDates: true) turns a field in ISO-8601 form into a real
DateTime during a typed decode, across decode, decodeToTable, decodeToMaps,
the streaming CsvDecoder, and bindBytes. Off by default.

Every date and time field is range-checked before parsing, so an impossible
value stays text instead of becoming the wrong date: DateTime.parse rolls
2024-13-45 over to 14 February 2025, and this does not. Ambiguous locale
formats, unpunctuated runs such as 20240131, and quoted fields all stay text.

Closes the only entry in the README's Limitations list. Adds a docs page at
/csv-dates and corrects the type-inference FAQ, which named a flag
(inferTypes) that does not exist.