Add reference-servers-maintainers GitHub team with admin on servers repo (#88)

- Expand REFERENCE_SERVERS_MAINTAINERS role (previously Discord-only) to
  create a GitHub team
- Grant the team admin permission on modelcontextprotocol/servers
- Add tobinsouth as a new member

Existing members cliffhall and olaservo will also be added to the new
GitHub team.

🏠 Remote-Dev: homespace

src/config/roles.ts

@@ -127,8 +127,8 @@ export const ROLES: readonly Role[] = [
   {
     id: ROLE_IDS.REFERENCE_SERVERS_MAINTAINERS,
     description: 'Reference servers maintainers',
+    github: { team: 'reference-servers-maintainers' },
     discord: { role: 'reference servers maintainers (synced)' },
-    // Discord only for now
   },
   {
     id: ROLE_IDS.REGISTRY_MAINTAINERS,