docs/zh_CN: add zh_CN/arch.rst

Add an entry for all zh arch documents.
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/4e9675ac83a06f2597d069f44a94c4e2cbd7ab2b.1665467392.git.bobwxc@email.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/arch.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+处理器体系结构
+==============
+
+以下文档提供了具体架构实现的编程细节。
+
+.. toctree::
+   :maxdepth: 2
+
+   mips/index
+   arm64/index
+   riscv/index
+   openrisc/index
+   parisc/index
+   loongarch/index
+
+TODOList:
+
+* arm/index
+* ia64/index
+* m68k/index
+* nios2/index
+* powerpc/index
+* s390/index
+* sh/index
+* sparc/index
+* x86/index
+* xtensa/index