Add one R preview bot.

Bug: skia:10371
Change-Id: I3e5c8b34b7b80fff492de11ec769b33e2be3671c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302577
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
4 files changed