Fix formatting of USERS.md

USERS.md

@@ -2,6 +2,7 @@ This document lists users of RocksDB and their use cases. If you are using Rocks
 
 ## Facebook
 At Facebook, we use RocksDB as a backend for many different stateful services. We're also experimenting with running RocksDB as a storage engine for two databases:
+
 1. MyRocks -- https://github.com/MySQLOnRocksDB/mysql-5.6
 2. MongoRocks -- https://github.com/mongodb-partners/mongo-rocks