[FEATURE] Bot Typing indicators

[dlassalle]

< Requires UIKit to enable in-app setting of typing indicators >

• Add configurable delay time between messages (will probably be around 0.8s) so user is not overwhelmed by multiple messages at once
• Activate the typing indicator when requests go outbound to dialogflow, then deactivate when we get our response back
• Add typing indicator for delays for followup event payloads (this would just be a toggle on, and would deactivate on the next message sent from either party)

DF custom payload:

{
  "followup": {
    "event": "event_name",
    "delay": 5000
  }
}