All-Projects: add commit_message_validator.json

This is used in the commit_message_validator plugin to verify that
trailers are present in commit messages.

BUG=b/291595251

Change-Id: I7bc7462e9cbb04d9fb0ebfce16cffbe88ac00f85
Reviewed-on: https://cos-review.googlesource.com/c/All-Projects/+/65191
Tested-by: Kevin Berry <kpberry@google.com>
Reviewed-by: Nandhini Rengaraj <nrengaraj@google.com>
2 files changed