New text is moved over from BlinkGCDesign.md

Bug: chromium:1283934
Change-Id: I10a84c91a642e96c494d6e523d6d89059afaa1ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3366658Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78498}