image: add codereview.cfg
image: add codereview.cfg

See golang.org/cl/4131 for context.

Change-Id: If30a8f22fe02ef58e94ee3c90afc065d9cd954d0
Reviewed-on: https://go-review.googlesource.com/7723
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

golang/image