(re-)add dsinclair to OWNERS

Change-Id: I8d550c61336a1151109e162b09b38e85d7eb4cfe
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/104701
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/OWNERS b/OWNERS
index 18239af..ce0a26e 100644
--- a/OWNERS
+++ b/OWNERS
@@ -3,5 +3,6 @@
 bclayton@google.com
 cwallez@chromium.org
 dneto@google.com
+dsinclair@google.com
 jrprice@google.com
 rharrison@chromium.org