Added a note to show about reorganize and autocommit

Author: rrg92

docs/t-sql/statements/alter-index-transact-sql.md

@@ -251,6 +251,7 @@ PARTITION
  REORGANIZE a **rowstore** index  
  For rowstore indexes, REORGANIZE specifies to reorganize the index leaf level. The REORGANIZE operation is:  
 
+-   Always performed online. This means long-term blocking table locks are not held and queries or updates to the underlying table can continue during the ALTER INDEX REORGANIZE transaction.  
 -   Not allowed for a disabled index  
 -   Not allowed when ALLOW_PAGE_LOCKS is set to OFF  
 -   Not rolled back when it is performed within a transaction and the transaction is rolled back.