[Feature Request] Update schedules example to retrieve `TemporalScheduledStartTime` search attribute

[cretz]

Describe the solution you'd like

In the schedule sample, show how you can get TemporalScheduledStartTime in a workflow

[jakejscott]

For context this is how it is done in the Go sample: https://github.com/temporalio/samples-go/blob/main/schedule/workflow.go