DOCSP-42813: codecs (mongodb#43)

* DOCSP-42813: codecs

* include errors

* wip

* vale

* wip

* SA PR fixes 1

* add cross link

Author: rustagir

source/data-formats.txt

@@ -22,6 +22,7 @@ Specialized Data Formats
    :maxdepth: 1
 
    /data-formats/serialization
+   /data-formats/codecs
    /data-formats/bson
    /data-formats/time-series
 
@@ -37,6 +38,10 @@ library to convert between MongoDB documents and different data formats
 in your application. To learn more about serialization, see the
 :ref:`kotlin-sync-serialization` guide.
 
+As an alternative to using {+language+} serialization, you can define
+and implement custom ``Codec`` types to support encoding and decoding of
+your {+language+} objects. To learn more, see the :ref:`kotlin-sync-codecs` guide.
+
 You can use several types of specialized document data formats in your
 application. To learn how to work with these data formats, see the following
 sections: