C: add Yan Zou (Google CLA).

R=adg

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/86930043

CONTRIBUTORS

@@ -555,6 +555,7 @@ William Chan <willchan@chromium.org>
 William Josephson <wjosephson@gmail.com>
 William Orr <will@worrbase.com> <ay1244@gmail.com>
 Xing Xing <mikespook@gmail.com>
+Yan Zou <yzou@google.com>
 Yasuhiro Matsumoto <mattn.jp@gmail.com>
 Yissakhar Z. Beck <yissakhar.beck@gmail.com>
 Yongjian Xu <i3dmaster@gmail.com>