docs/zh_CN: add damon design translation

Translate .../vm/damon/design.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/2685ed7d446620b260c20158685728c3adb5e0fe.1642230669.git.siyanteng@loongson.cn


Signed-off-by: Jonathan Corbet <corbet@lwn.net>