Add contributors to CONTRIBUTORS.
Add contributors to CONTRIBUTORS.

These people have contributed and reviewed significant and non-trivial
code.

R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/995893002

hankbao/Crashpad,chromium/crashpad,chromium/crashpad,atom/crashpad,chromium/crashpad,Chilledheart/crashpad,hokein/crashpad,atom/crashpad,Chilledheart/crashpad,Chilledheart/crashpad,hankbao/Crashpad,hankbao/Crashpad,atom/crashpad,hokein/crashpad,hokein/crashpad