[web snapshot] Add cbruni@ to OWNERS

No-Try: true
Change-Id: I8ba97cd2fe3ba0b7fa23960aa2ed9880454996a4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2933660Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74931}

src/web-snapshot/OWNERS

+cbruni@chromium.org
 marja@chromium.org
 leszeks@chromium.org
 syg@chromium.org