Update HISTORY.md for option to make write group size configurable (#5798)

Summary:
Update HISTORY.md for option to make write group size configurable .
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5798

Differential Revision: D17369062

fbshipit-source-id: 390a3fa0b01675e91879486a729cf2cc7624d106

HISTORY.md

@@ -6,6 +6,7 @@
 * Fix bloom filter lookups by the MultiGet batching API when BlockBasedTableOptions::whole_key_filtering is false, by checking that a key is in the perfix_extractor domain and extracting the prefix before looking up.
 * Fix a bug in file ingestion caused by incorrect file number allocation when the number of column families involved in the ingestion exceeds 2.
 ### New Features
+* Introduced DBOptions::max_write_batch_group_size_bytes to configure maximum limit on number of bytes that are written in a single batch of WAL or memtable write. It is followed when the leader write size is larger than 1/8 of this limit.
 * VerifyChecksum() by default will issue readahead. Allow ReadOptions to be passed in to those functions to override the readhead size. For checksum verifying before external SST file ingestion, a new option IngestExternalFileOptions.verify_checksums_readahead_size, is added for this readahead setting.
 * When user uses options.force_consistency_check in RocksDb, instead of crashing the process, we now pass the error back to the users without killing the process.
 ### Public API Change