Explicitly state that the Chromium Code of Conduct also applies to V8

R=danno@chromium.org,rschoen@chromium.org,seththompson@chromium.org
BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/1754723002

Cr-Commit-Position: refs/heads/master@{#34421}

CODE_OF_CONDUCT.md

+# V8 Code of Conduct
+
+As part of the Chromium team, the V8 team is committed to preserving and
+fostering a diverse, welcoming community. To this end, the [Chromium Code of
+Conduct](https://chromium.googlesource.com/chromium/src/+/master/CODE_OF_CONDUCT.md)
+applies to our repos and organizations, mailing lists, blog content, and any
+other Chromium-supported communication group, as well as any private
+communication initiated in the context of these spaces.