We don't accept PRs via GH, so add a job to automatically close them
with an explanation for how to submit.
Change-Id: I5cc3176549a04ff23b04dae1110cd27a58ba1fd3
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/386134
Tested-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
