These are the v2 docs. For the current version, look here.

teams

A pro plan is required to use this feature on private repos.

The GitHub teams whose members make up this reviewer group. Be sure to use the slug (lowercase, hyphenated) for the team names. Currently, the teams must have explicit access to the repo (via repo settings).

A reviewer group must use either users or teams, but not both.

Example usage:

groups:
  designers:
    teams:
      - security-reviewers
      - code-review