Implement spectator functions for lobbies

[jiyeongchloe]

Goal: According to the user stories, there should be an option for users to spectate a lobby whose match has not finished yet. We currently do not have functionalities to support spectating. We need to change the Lobby model to account for spectators, not just players, implement spectate lobby and stop spectating lobby buttons, and implement a spectator status bar that appears at the top of a lobby details page when a user decides to spectate.

Deliverables:

• Update to the Matches ERD page
• Pull Request