Add kristipark to components/ntp_tiles/OWNERS

Change-Id: Ic7b851d7330c1f2bded6fce997119412556657e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578547
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Kristi Park <kristipark@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653273}

components/ntp_tiles/OWNERS

 fhorschig@chromium.org
 jkrcal@chromium.org
+kristipark@chromium.org
 mastiz@chromium.org
 treib@chromium.org