Add rich entity suggestion to showcase

Currently, this doesn't do much because showcase has no way to fetch the
image, but the URL is there just in case.

Bug: 966429
Change-Id: I34f7bf7a329e60774c7ca314994e86123dae451d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627374
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663083}
3 files changed