Add "pending" flag for deferred interaction responses

[i0bs]

Deferred interaction responses are already used by many bot developers to pause the final response of an interaction. Adding a flag to signify that it's still pending a final response of some sort can be very useful to avoid spamming an interaction through a slash command or component.

My proposal is that with a flag on the interaction, bots can search up any given interaction still ongoing through the invoker to see if it has finished or not, giving developers the power to stop their users from lining up a series of interaction responses that might stress their application in terms of performance or other factors.

This is different from a callback type as they are already being used to determine the kind of interaction being processed. This change would be proposed as going under the Interaction resource object as a flags field, where PENDING becomes 0 << 1. The interaction callback data would also have to theoretically supply this field as well so developers could create some sort of internal relationship between the ID and field setting.