DOCSP-27090 Add Atlas only stage note (#449)

* DOCSP-27090 Add Atlas only stage note

* additional

* terminology:

* ,

* fix backticks on command-line-options page

* Internal Review Feedback

* fix link

* space

* add detail sentence

* link

* link

* link

* link

Author: ianf-mongodb

source/aggregation-pipeline-builder.txt

@@ -31,6 +31,18 @@ aggregation pipeline. The :guilabel:`Preview of Documents in the
 Collection` section shows 20 documents randomly sampled from the chosen
 collection.
 
+.. note:: Atlas Search Stages
+
+   When you connect |compass-short| to a MongoDB deployment hosted on 
+   `Atlas <https://www.mongodb.com/cloud/atlas?tck=docs_compass>`_,
+   additional Atlas-only stages 
+   :atlas:`$search </reference/atlas-search/query-syntax/#-search>` and
+   :atlas:`$searchMeta </reference/atlas-search/query-syntax/#-searchmeta>`
+   are available in the Aggregation Pipeline Builder. Use these stages 
+   to perform 
+   :atlas:`full-text search</atlas-search/atlas-search-overview>` 
+   on Atlas collections.
+
 Tasks
 -----