docs/zh_CN: link programming-language into process/index

It could be found in index now.
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Harry Wei <harryxiyou@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/process/index.rst

@@ -26,6 +26,7 @@
    code-of-conduct
    code-of-conduct-interpretation
    submitting-patches
+   programming-language
    coding-style
    development-process
    email-clients