YAML config doesn't support all time formats on maxAge

[DavidHoessle]

The yaml config doesn't seem to support any time specification above hour (h) such as d for day, M for month and y for year.

nack/controllers/jetstream/stream.go

Lines 572 to 578 in 6c54a4e

	func getMaxAge(v string) (time.Duration, error) {
	if v == "" {
	return time.Duration(0), nil
	}
	return time.ParseDuration(v)
	}