Worker: Add README file to core/workers

Bug: 837127
Change-Id: Iee15da96b578ca1385440716ae5b733f30559f68
Reviewed-on: https://chromium-review.googlesource.com/1029564
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553937}
1 file changed