Optional
commandBy default, the followup goes to the same participant/command. But this property can be set to invoke a different command.
Optional
labelA title to show the user. The prompt will be shown by default, when this is unspecified.
Optional
participantBy default, the followup goes to the same participant/command. But this property can be set to invoke a different participant by ID. Followups can only invoke a participant that was contributed by the same extension.
The message to send to the chat.
A followup question suggested by the participant.
Stubbed