Update documentation explainning how to configure the different replication modes

The current Administration Manual section doesn't explain how to set the SG replication features

https://stackgres.io/doc/latest/administration/

One suggestion is adding a Replication item in the list after High Availability

• Administration Manual
  • Replication
    • mode
      • async
      • sync
      • strict-sync
      • sync-all
      • strict-sync-all
      • group replication
    • role
      • ha
      • ha-read
      • readonly
      • none
  • Remote Cluster
    • ReplicateFrom
      • StandbyLeader