docs/zh_CN: link the CoC into process/index

Let it appears in html links.
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

@@ -23,6 +23,7 @@
    :maxdepth: 1
 
    howto
+   code-of-conduct
    submitting-patches
    coding-style
    development-process