Add fgorski to image_fetcher OWNERS

Change-Id: I7af13ac123280be7b4b89a3b05918e2b8ea96ce3
Reviewed-on: https://chromium-review.googlesource.com/1208819Reviewed-by: Filip Gorski <fgorski@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Reviewed-by: Markus Heintz <markusheintz@chromium.org>
Commit-Queue: Markus Heintz <markusheintz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589462}

components/image_fetcher/OWNERS

+fgorski@chromium.org
 markusheintz@chromium.org
 mathp@chromium.org
 treib@chromium.org