Add Nan Zhou as a reviewer

As requested by current maintainers in the following change,
[1] https://gerrit.openbmc.org/c/openbmc/phosphor-user-manager/+/58675

Add myself to the reviewer list so I can become a maintainer one day.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: Ie2102487873df88c28dedb3e4daaff8a345b9e11
diff --git a/OWNERS b/OWNERS
index 148337d..3df483d 100644
--- a/OWNERS
+++ b/OWNERS
@@ -36,6 +36,7 @@
 - richard.marian.thomaiyar@linux.intel.com
 
 reviewers:
+- nanzhoumails@gmail.com
 
 matchers: