[infra] Add test directory to test OWNERS enforcement

No-Try: true
Bug: chromium:1235962
Change-Id: I4ed07e9e39ae60fa24b76b40bf8d251d16c924e7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3067336
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Liviu Rau <liviurau@chromium.org>
Reviewed-by: Liviu Rau <liviurau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76049}

infra/playground/OWNERS

+set noparent
+
+almuthanna@chromium.org
+liviurau@chromium.org
+tmrts@chromium.org
\ No newline at end of file

infra/playground/README.md

+This directory's purpose is test OWNERS enforcement.
\ No newline at end of file