Default endpoint does not include events that are sold out or only announced

The `events/search` endpoint doesn't include events that are sold out or only announced, but these _are_ available on this endpoint by passing an empty `q` query param:

`https://www.eventbriteapi.com/v3/events/search/?q=+&organizer.id=&token=`

A new `Eventbrite_Query` argument could be added that triggers the empty param, maybe just `soldout_announced = true`.

Start by locating the Eventbrite_Query handling for the events/search endpoint and compare its default request with the documented empty q query parameter. Confirm the change makes sold-out and announced events appear without breaking existing searches, then verify the endpoint behavior with the repository's available checks.

Written by the indexing model from the issue text.