CONTRIBUTORS: add Luuk van Dijk (Google CLA)

R=lvd
CC=golang-dev
https://golang.org/cl/1956046
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 63ffcca..b949e53 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -97,6 +97,7 @@
 Kirklin McDonald <kirklin.mcdonald@gmail.com>
 Kyle Consalus <consalus@gmail.com>
 Larry Hosken <lahosken@golang.org>
+Luuk van Dijk <lvd@golang.org> <lvd@google.com>
 Mark Zavislak <zavislak@google.com>
 Markus Duft <markus.duft@salomon.at>
 Mathieu Lonjaret <mathieu.lonjaret@gmail.com>