Create a dropdown menu in the Lobby to select a demo scene

[RGonzalezTech]

Are you willing to refactor the lobby a bit so that it has a dropdown instead? I figure this can be part of a larger "demo selection" process.

Originally posted by @RGonzalezTech in #9 (comment)

blocked by #9

[RGonzalezTech]

The lobby scene should be responsible for handling level-select interactions and then switching the LobbyManager.current_lobby.active_scene_path to the proper scene res:// path.