ScheduleAt missing from CreateBookmarkArgs

## Description
In the currently available documentation it's stated the following

4. Scheduled Bookmarks and Timers
For time-based operations, use Elsa's built-in timer activities or scheduled bookmarks:
// Schedule a bookmark to execute at a specific time
var scheduledBookmark = context.CreateBookmark(new CreateBookmarkArgs
{
BookmarkName = "ScheduledTask",
Callback = OnScheduledTimeAsync,
ScheduledAt = DateTime.UtcNow.AddHours(24)
});

However in Elsa Workflows 3.6-rc.2 (at least) ScheduleAt property is missing from CreateBookmarkArgs class.
Considering the Api has changed since the documentation was written what's the currently recommended way in a custom activity to schedule a bookmark to start at a specific date and time?