chore: clickhousesystemtablesreceiver: add comment about cluster para…

…m in scrape config to Readme… (#327)

* chore: clickhousesystemtablesreceiver: add comment about cluster param in scrape config to Readme

* Update README.md

receiver/clickhousesystemtablesreceiver/README.md

@@ -13,10 +13,14 @@ receivers:
   clickhousesystemtablesreceiver:
     # required
     dsn: tcp://clickhouse:9000/
+
+    # optional. Should be set to name of the cluster when scraping query logs from a clustered Clickhouse deployment
+    cluster_name: "cluster-name"
+
     query_log_scrape_config:
       scrape_interval_seconds: 20
       # required. min_scrape_delay_seconds must be set to a duration larger
       # than flush_interval_milliseconds settings for query_log
       # For details, see https://clickhouse.com/docs/en/operations/server-configuration-parameters/settings#query-log
       min_scrape_delay_seconds: 8
-```
+```