DOCS-10757 Add page for error codes (#5319) (#6548)

* DOCS-10757 Add page for error codes (#5319)

* add error code page and update TOC

* removed obsolute and not-yet-available

* fix indentation error

Author: MongoCaleb

source/reference.txt

@@ -26,6 +26,9 @@ Reference
    Documentation of :binary:`~bin.mongod` and :binary:`~bin.mongos`
    and all other tools distributed with MongoDB.
 
+:ref:`server-error-codes`
+   Details the error codes that MongoDB returns.
+
 :doc:`/reference/configuration-options`
    Full documentation of the configuration file and available
    run-time operations.
@@ -100,8 +103,10 @@ Reference
    /reference/collation
    /reference/mongodb-wire-protocol
    /reference/log-messages
+   /reference/error-codes
    /reference/exit-codes
    /reference/glossary
    /reference/default-mongodb-port
    /reference/mongodb-defaults
    /reference/server-sessions
+