Give a little bit of introduction to Oilpan and provide a few links to
navigate the project.

Bug: chromium:1056170
Change-Id: I4ef8c256c8de7932e3393017be6c58ba48ca45f2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3114141
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76457}