(DOCSP-10473) As an author, I can specify a delimiter when concatenating arrays (#363)

* (DOCSP-10473): add description of delimiters for array concat

* (DOCSP-10473): add default delimiter

* (DOCSP-10473): formatting fix

* tech review feedback

Author: jwilliams-mongo

source/rich-schema-support.txt

@@ -95,6 +95,27 @@ You can apply these accumulates to arrays of String values:
 
    * - concat
      - Concatenates the values of the array into a a single string.
+       In the :guilabel:`Delimiter` field, enter characters that you
+       want |charts-short| to display between each array element. The
+       default delimiter is ``,``.
+
+       .. example::
+
+          Consider the following array that describes movie genres:
+
+          .. code-block:: javascript
+             :copyable: false
+
+             "genres": ["Action", "Horror", "Sci-Fi"]
+
+          |charts-short| concatenates the array to produce the following
+          string when you enter ``/`` in the :guilabel:`Delimiter`
+          field: 
+
+          .. code-block:: none
+             :copyable: false
+
+             Action/Horror/Sci-Fi
 
    * - min length
      - Returns the length of the shortest string in the array.