[COMMUNITY] Mark Shields -> Reviewer (apache#9369)

Author: yzhliu

CONTRIBUTORS.md

@@ -133,6 +133,7 @@ We do encourage everyone to work anything they are interested in.
 - [Junru Shao](https://github.com/junrushao1994): @junrushao1994
 - [Haichen Shen](https://github.com/icemelon9): @icemelon9
 - [Xingjian Shi](https://github.com/sxjscience): @sxjscience
+- [Mark Shields](https://github.com/mbs-octoml): @mbs-octoml
 - [Christopher Sidebottom](https://github.com/mousius): @mousius
 - [Siva Rama Krishna Reddy](https://github.com/srkreddy1238): @srkreddy1238
 - [Dmitriy Smirnov](https://github.com/d-smirnov): @d-smirnov