[COMMUNITY] kazum -> committer (#2831)

CONTRIBUTORS.md

@@ -19,6 +19,7 @@ We do encourage everyone to work anything they are interested in.
 - [Yizhi Liu](https://github.com/yzhliu) (PMC): @yzhliu - jvm, topi, relay
 - [Masahiro Masuda](https://github.com/masahi): @masahi - topi, relay
 - [Thierry Moreau](https://github.com/tmoreau89) (PMC): @tmoreau89 - vta
+- [Kazutaka Morita](https://github.com/kazum): @kazum - frontends, opencl
 - [Jared Roesch](https://github.com/jroesch): @jroesch - relay
 - [Siva](https://github.com/srkreddy1238): @srkreddy1238 - frontends, golang
 - [Haichen Shen](https://github.com/icemelon9) (PMC): @icemelon9 - relay, topi