Add "Timer" action in the bot builder

This could be usefull for multiple use cases, first for example when we face issues with the order of some messages (sometimes messages are not delivered in the right order); adding a timer of 2 seconds between certain messages would help making sure messages are delivered in the right order.

On top, a client using webhooks at the beginning of the bot says that once the contact is created he doesn't have "the time" to retrieve information from the contact that the bot is already acting (he is still manage to fix this via a work around). It would be useful for him add a Timer action at the very start of the bot so that the bot would take a few second more to take an action.