Add Microsoft Bing as a user (#11270)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/11270

Reviewed By: pdillinger

Differential Revision: D43811584

Pulled By: ajkr

fbshipit-source-id: f27e55395644a469840785685646456f6b1452fc

USERS.md

@@ -15,6 +15,9 @@ At Facebook, we use RocksDB as storage engines in multiple data management servi
 
 [2] https://code.facebook.com/posts/357056558062811/logdevice-a-distributed-data-store-for-logs/
 
+## Microsoft
+The Bing search engine from Microsoft uses RocksDB as the storage engine for its web data platform: https://blogs.bing.com/Engineering-Blog/october-2021/RocksDB-in-Microsoft-Bing
+
 ## LinkedIn
 Two different use cases at Linkedin are using RocksDB as a storage engine: