docs: update aggregator node documentation on wwebsite

Author: jpraynaud

docs/website/root/manual/develop/nodes/mithril-aggregator.md

@@ -542,6 +542,7 @@ Here is a list of the available parameters for the serve command:
 | `metrics_server_port`                                            | `--metrics-server-port`                                            |          -           | `METRICS_SERVER_PORT`                                                                                     | Metrics HTTP server listening port                                                                                                                                                                       | `9090`                                        | -                                                                                                                                                                                                                                                                                                |                        -                        |
 | `persist_usage_report_interval_in_seconds`                       |                                                                    |          -           | `PERSIST_USAGE_REPORT_INTERVAL_IN_SECONDS`                                                                | Duration in seconds between two recording of usage metrics                                                                                                                                               | `10`                                          | `5`                                                                                                                                                                                                                                                                                              |                        -                        |
 | `leader_aggregator_endpoint`                                     | `--leader-aggregator-endpoint`                                     |          -           | `LEADER_AGGREGATOR_ENDPOINT`                                                                              | Leader aggregator endpoint (used with unstable feature)                                                                                                                                                  | -                                             | `https://aggregator.pre-release-preview.api.mithril.network/aggregator`                                                                                                                                                                                                                          |                        -                        |
+| `aggregate_signature_type`                                       | -                                                                  |          -           | `AGGREGATE_SIGNATURE_TYPE`                                                                                | Aggregate signature type used to create certificates                                                                                                                                                     | `Concatenation`                               | -                                                                                                                                                                                                                                                                                                |               :heavy_check_mark:                |
 
 `genesis bootstrap` command: