Add Xinhao as a code owner. (#97)

diff --git a/CODEOWNERS b/CODEOWNERS
index fbd9c1c..e3194e0 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-*   @asraa @inferno-chromium @markus-kusano @oliverchang @stefanbucur
+*   @asraa @inferno-chromium @markus-kusano @oliverchang @stefanbucur @xinhaoyuan