adding brettmthompson as approver and reviewer in OWNERS file (#79)

Signed-off-by: Brett Thompson <[email protected]>

Author: brettmthompson

OWNERS

@@ -1,4 +1,5 @@
 approvers:
+  - brettmthompson
   - danielezonca
   - hdefazio
   - israel-hdez
@@ -10,6 +11,7 @@ approvers:
   - terrytangyuan
   - VedantMahabaleshwarkar
 reviewers:
+  - brettmthompson
   - hdefazio
   - israel-hdez
   - Jooho
@@ -18,4 +20,4 @@ reviewers:
   - rnetser
   - spolti
   - terrytangyuan
-  - VedantMahabaleshwarkar
+  - VedantMahabaleshwarkar