introduce facilitator role

[vanderhoop]

As a retro creator who believes a retro should always have a guiding hand,
I would like the retrospective user with the earliest arrival timestamp to be given the role of facilitator,
So that they may guide the retrospective participants through the course of the retro.

Acceptance Criteria:

• upon entering a room, there is text beside the name of the user who joined the room earliest
  • example: "Travis (Facilitator)"
• when a facilitator leaves the room, the facilitator role automatically shifts to the user with the next earliest arrival timestamp