This Cl updates the .gitignore with the .gclient and .gclient_entries
files.
Bug: tint:12
Change-Id: I645016ca83396c0616f2ad3f69d2ce510be59b53
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/16580
Reviewed-by: Ryan Harrison <rharrison@chromium.org>