Description in the changelog about changefeed backup/restore (#12840)

ydb/apps/ydb/CHANGELOG.md

@@ -1,3 +1,4 @@
+* Backup and restore of changefeeds has been added to `ydb tools dump` and `ydb tools restore`. As a result, there are changes in the backup file structure: for tables with changefeeds, a subdirectory is created for each changefeed, named after the changefeed. This subdirectory contains two files: `changefeed_description.pb`, which contains the changefeed description, and `topic_description.pb`, which contains information about the underlying topic.
 * Added `--skip-checksum-validation` option to `ydb import s3` command to skip server-side checksum validation.
 
 ## 2.18.0 ##