DOCSP-35829-new-districtmany-method (mongodb#367)

(cherry picked from commit 65e9142)

Author: gmiller-mdb

source/fundamentals/linq.txt

@@ -804,6 +804,12 @@ implementation of LINQ:
    * - ``Distinct``
      - Returns distinct documents that match the specified criteria
 
+   * - ``DistinctMany``
+     - Returns distinct documents from an array that match the specified criteria
+
+   * - ``Exists``
+     - Tests whether a field exists
+
    * - ``First``
      - Returns the first matching document, and throws an exception if none are found