add Tombstone property (#847)

modules/reference/pages/properties/cluster-properties.adoc

@@ -4878,6 +4878,26 @@ Transaction manager's synchronization timeout. Maximum time to wait for internal
 
 ---
 
+=== tombstone_retention_ms
+
+The retention time for tombstone records in a compacted topic. Cannot be enabled at the same time as any of `cloud_storage_enabled`, `cloud_storage_enable_remote_read`, or `cloud_storage_enable_remote_write`. A typical default setting is `86400000`, or 24 hours.
+
+*Unit:* milliseconds
+
+*Requires restart:* No
+
+*Visibility:* `user`
+
+*Type:* integer
+
+*Accepted values:* [`1`, `17592186044415`]
+
+*Default:* `null`
+
+*Related topics:* xref:manage:cluster-maintenance/compaction-settings.adoc#tombstone-record-removal[Tombstone record removal]
+
+---
+
 === topic_fds_per_partition
 
 Required file handles per partition when creating topics.