CONTRIBUTORS: add Cherry Zhang (Google CLA)
CONTRIBUTORS: add Cherry Zhang (Google CLA)

Change-Id: I4efd109b864869e5069f69847f64a55cd1ac053d
Reviewed-on: https://go-review.googlesource.com/64111
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend