Add saschagrunert and zhangguanzhang to OWNERS

Adding a couple of more community members to the OWNERS file.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

OWNERS

@@ -3,22 +3,26 @@ approvers:
   - edsantiago
   - giuseppe
   - jwhonce
+  - Luap99
   - mheon
   - rhatdan
+  - saschagrunert
   - TomSweeneyRedHat
-  - vrothberg
   - umohnani8
-  - Luap99
+  - vrothberg
+  - zhangguanzhang
 reviewers:
+  - ashley-cui
   - baude
   - edsantiago
   - giuseppe
   - jwhonce
-  - mheon
-  - rhatdan
-  - TomSweeneyRedHat
-  - vrothberg
-  - ashley-cui
-  - QiWang19
-  - umohnani8
   - Luap99
+  - mheon
+  - QiWang19
+  - rhatdan
+  - saschagrunert
+  - TomSweeneyRedHat
+  - umohnani8
+  - vrothberg
+  - zhangguanzhang