Add OWNERS to Chromium codelab

- Retain "*" as owner
- Add primary/secondary owner(s)

Bug: N/A
Change-Id: Iab132e93d107ea6870bef09e40f7d0bc883280d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2486076Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#818640}

codelabs/OWNERS

-*
+*
\ No newline at end of file
+
+# Primary
+pwnall@chromium.org
\ No newline at end of file