DOCSP-37440: documentdb feedback on indexes (#949)

* DOCSP-37440: documentdb feedback on indexes

* MW PR fixes 1

Author: rustagir

source/documentdb-support.txt

@@ -69,6 +69,16 @@ available in a limited capacity or are not supported at all:
   ``$toObjectId``, ``$toString``, ``$isNumber``, ``$rand``, ``$sampleRate``, ``$getField``
 - **Aggregation Stages**: ``$collStats``, ``$facet``, ``$bucket``, ``$bucketAuto``,
   ``$sortByCount``, ``$listLocalSessions``, ``$listSessions``, ``$graphLookup``
+  
+In addition, Amazon DocumentDB does not leverage indexes when you perform
+queries that contain any of the following operators:
+
+- ``$ne``
+- ``$nin``
+- ``$nor``
+- ``$not``
+- ``$exists``
+- ``$elemMatch``
 
 To learn more about Amazon DocumentDB's compatibility with MongoDB v4.0 and MongoDB v5.0,
 see the following AWS documentation: