Add Vietnamese translation details to documentation

Author: tamnd

documentation/translations/translating.rst

@@ -118,7 +118,10 @@ For more details about translations and their progress, see
      - Dmytro Kazanzhy (:github-user:`kazanzhy`, `email <mailto:dkazanzhy@gmail.com>`__)
      - :github:`GitHub <python/python-docs-uk>`,
        `Transifex <tx_>`_
-
+   * - `Vietnamese (vi) <https://docs.python.org/vi/>`__
+     - Duc-Tam Nguyen (:github-user:`tamnd`)
+     - :github:`GitHub <tamnd/python-docs-vi>`,
+       `Transifex <https://www.transifex.com/>`__
 
 How to get help
 ===============