[d8][owners] Add cbruni as src/d8 owner

Change-Id: Ib34bb9aeeab0e092cdfa49da11382cdb5a8a20e3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2545709Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71329}

src/d8/OWNERS

 binji@chromium.org
 bmeurer@chromium.org
+cbruni@chromium.org
 clemensb@chromium.org
 ulan@chromium.org
 verwaest@chromium.org