Append operation summary

Author: osipovartem

iceberg-rust/src/table/transaction/append.rs

@@ -210,4 +210,4 @@ pub(crate) fn append_summary(files: &[DataFile]) -> Option<HashMap<String, Strin
         ("added-records".into(), added_records.to_string()),
         ("added-data-files".into(), added_data_files.to_string()),
     ]))
-}
+}