DOCSP-14925 Change isMaster to hello (#131)

* DOCSP-14925 Change isMaster to hello

* DOCSP-14925 updates for external review feedback

Author: kanchana-mongodb

source/supported-unsupported/mql-support.txt

@@ -318,10 +318,20 @@ Replication Commands
    * - :manual:`isMaster </reference/command/isMaster>`
 
      - The response always returns a document in which
-       ``isMaster: true``. It also returns operational parameters.
+       ``isMaster: true``. It also returns operational parameters. 
 
-       The optional saslSupportedMechs field set to the <db.user> is
-       supported.
+       The optional ``saslSupportedMechs`` field set to the 
+       ``<db.user>`` is supported.
+
+       .. note:: About the ``hello`` Command
+
+          {+adl+} also supports the ``hello`` command, which is an 
+          alias for the ``isMaster`` command. The ``hello`` command 
+          returns a document that is identical to the document 
+          returned by the ``isMaster`` command. In the document 
+          returned by the ``hello`` command, the ``isWritablePrimary`` 
+          field is set to ``true`` instead of the ``isMaster`` field. 
+          We recommend the ``hello`` command instead of ``isMaster``.
 
 Administration Commands
 -----------------------