DOCSP-18741 Release Notes v1.20.0 (#630)

* DOCSP-18741 Release Notes v1.20.0

* DOCSP-18741 updates for copy review feedback

Author: kanchana-mongodb

source/release-notes.txt

@@ -14,6 +14,34 @@ Release Notes for {+mcli-long+}
    :depth: 1
    :class: singlecol
 
+.. _mcli_1.20.0:
+
+{+mcli+} 1.20.0
+------------------
+
+*Released 2021-09-16*
+
+New Features
+~~~~~~~~~~~~
+
+- Adds support for creating |service| ``M0`` cluster using the 
+  :ref:`mongocli-atlas-quickstart` and 
+  :ref:`mongocli-atlas-clusters-create` commands.
+- Adds support for creating serverless |service| clusters.
+- Adds support for downloading |service| access logs.
+- Adds support for enabling |service| management of the slow operation 
+  threshold for your cluster.
+- Validates the feature compatibility level against |onprem| versions.
+- Adds support for cloud data migrations.
+- Displays a message when a new version is available, which you can 
+  disable by running ``mongocli config set skip_update_check true``.
+
+Fixes and Improvements
+~~~~~~~~~~~~~~~~~~~~~~
+
+- Includes small improvements to the :ref:`mongocli-atlas-quickstart` 
+  command.
+
 .. _mcli_1.19.0:
 
 {+mcli+} 1.19.0