Add zh_HANS language mapping to locale config

conf/locale/config.yaml

 # Configuration for i18n workflow.
 
+# This will copy each source language to a new directory at the end of the i18n generate step
+# which allows us to migrate to a new locale code without re-creating the Transifex project.
+edx-lang-map:
+    zh_CN: zh_HANS
+
 locales:
     - en  # English - Source Language
     # - am  # Amharic