Ability to add child teams

As title says 🙂

It would be advantageous if this bot could support nesting Teams.

The team sync yaml could be enhanced to support something like the following:

```yml
# This property is used to control the addition of general Members to your Organization.
OrganizationMembersGroup: Some_Group_To_Sync_For_Organization_Membership
# This property is used for syncing all other GitHub Teams. Please note that users must also be a part of the `OrganizationMembersGroup` for the synchronization of the teams below to function properly.
GitHubTeamNames:
- Team: Some_Team_To_Sync
FollowChildren: true
- Team: Some_Other_Team_To_Sync
Children:
- Team: Some_Child_Team_To_Sync
Children: Some_Child_Team_To_Sync
- Some_Other_Child_Team_To_Sync
```

En el issue no se mencionan archivos fuente, pruebas ni puntos de entrada. Empieza por localizar la configuración YAML de sincronización de equipos y el código que procesa GitHubTeamNames; define cómo deben comportarse los Children y FollowChildren anidados y, a continuación, verifica que los equipos anidados se sincronicen según lo previsto.

Escrito por el modelo de indexación a partir del texto del issue.