[zh]translation of 12-3.md (Atcold#559)

* Add files via upload

* Update 12-3.md

* Update _config.yml

Co-authored-by: Alfredo Canziani <[email protected]>

Author: Tangshengku

docs/_config.yml

@@ -176,6 +176,7 @@ zh:
       sections:
         - path: zh/week12/12-1.md
         - path: zh/week12/12-2.md
+        - path: zh/week12/12-3.md
     - path: zh/week13/13.md
         - path: zh/week13/13-1.md
     - path: zh/week14/14.md