docs/zh_CN: Add translation zh_CN/doc-guide/sphinx.rst

Add new translation
  Documentation/translations/zh_CN/doc-guide/sphinx.rst
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/7c8c2eeb6c0b73410fbdb66cf702dc0e58b02a3e.1618295149.git.bobwxc@email.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>