Add syg@ to src/d8/OWNERS

Change-Id: I98f9808c139cb0f04efae2d732e9ed60e6d2d78b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3278678
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82788}

src/d8/OWNERS

 cbruni@chromium.org
 clemensb@chromium.org
 marja@chromium.org
+syg@chromium.org
 verwaest@chromium.org