default boolean addReplicator(final PeerId peer) {
        return addReplicator(peer, ReplicatorType.Follower);
    }
Adds a replicator for follower({@link ReplicatorType#Follower}).
@see #addReplicator(PeerId, ReplicatorType)

@param peer target peer
@return true on success
jraft-core/src/main/java/com/alipay/sofa/jraft/ReplicatorGroup.java