DOCS-15428 v5.3 (#1329)

* DOCS-15428 add documents to agg ref page

* CR1 Feedback

Author: ianf-mongodb

source/includes/extracts-agg-stages.yaml

@@ -291,4 +291,8 @@ content: |
           connected :binary:`~bin.mongos` or :binary:`~bin.mongod`
           instance. These sessions may have not yet propagated to the
           ``system.sessions`` collection.
+      
+      * - :pipeline:`$documents`
+
+        - Returns literal documents from input values.
 ...

source/reference/operator/aggregation-pipeline.txt

@@ -34,8 +34,7 @@ For aggregation expression operators to use in the pipeline stages, see
 ``db.aggregate()`` Stages
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Starting in version 3.6, MongoDB also provides the
-:method:`db.aggregate` method:
+MongoDB also provides the :method:`db.aggregate` method:
 
 .. code-block:: javascript
 
@@ -110,6 +109,9 @@ Alphabetical Listing of Stages
 
      - .. include:: /includes/fact-densify-description.rst
 
+   * - :pipeline:`$documents`
+
+     - Returns literal documents from input values.
 
    * - :pipeline:`$facet`