Support endpoints/fields for team-race feature

[sg4e]

Racetime.gg added support for team races on April 5, 2021. New fields and endpoints became available, but the documentation is not yet completed. It's possible more team-racing features will be added later too. Quoted from Dyn:

Race detail endpoint:

• Added team_race (bool): indicator if this is a team race.
• Added require_even_teams (bool): indicates race requires all teams to have the same number of participants.
• Added allow_prerace_chat (bool): indicates users may chat during race preparation.
• Added team (object) to the entrants list (see documentation for more details).
• Entrant actions may now include the 'set_team' action.

Team detail endpoint:

• Added (see documentation for more details).