[ios] Creates OWNERS file for ios/showcase/infobars

I've created the directory and have been involved in every contribution
to it so far.

Bug: 911864
Change-Id: I6a40424094d7f73eab46c48f20423da8614db46c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648910Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667329}

ios/showcase/infobars/OWNERS

+sczs@chromium.org
+
+# TEAM: ios-directory-owners@chromium.org
+# OS: iOS