Inside `timestamp(...)`: uses `chrono::DateTime<Local>` instead of `SystemTime`
as the injected timestamp type (default: off). Opt-in, and needs oopsie's
`chrono` feature enabled.
Forms: `chrono`, `chrono = true`, `chrono = false`, `chrono(true)`,
`chrono(false)`.
### Example
```ignore
// `chrono = true` only compiles with oopsie's `chrono` feature, which this
// crate's own doctests don't enable.
#[oopsie::oopsie(traced(timestamp(chrono = true)))]
pub enum AppError {
#[oopsie("boom")]
Boom,
}
```