docs/zh_CN: add process maintainer-pgp-guide tanslation

Translate process/maintainer-pgp-guide.rst into Chinese.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/7c7f24f653468c9a2c7e3909a7a390ea36eec879.1700474235.git.siyanteng@loongson.cn

Documentation/translations/zh_CN/process/index.rst

@@ -29,6 +29,7 @@
    submitting-patches
    programming-language
    coding-style
+   maintainer-pgp-guide
    development-process
    email-clients
    license-rules