[presubmit] Add PRESUBMIT.py

https://crbug.com/1032231

Change-Id: I81827754ae95bfef980963953a35206681037b1d
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/137983
Reviewed-by: Robbie Iannucci <iannucci@google.com>
2 files changed