Add example in config doc

Author: hachikuji

kafka-client/src/main/java/dev/responsive/kafka/api/config/ResponsiveConfig.java

@@ -129,7 +129,7 @@ public class ResponsiveConfig extends AbstractConfig {
   private static final String RS3_PORT_DOC = "The port to use when connecting to RS3.";
 
   public static final String RS3_LOGICAL_STORE_MAPPING_CONFIG = "responsive.rs3.logical.store.mapping";
-  public static final String RS3_LOGICAL_STORE_MAPPING_DOC = "Mapping from table name to RS3 logical store ID";
+  public static final String RS3_LOGICAL_STORE_MAPPING_DOC = "Mapping from table name to RS3 logical store ID (e.g. 'table:b1a45157-e2f0-4698-be0e-5bf3a9b8e9d1,...')";
 
   // ------------------ ScyllaDB specific configurations ----------------------