Update blink/renderer/README.md

Add a link to a "How Blink works" document to README.md.

TBR=thakis@chromium.org

Change-Id: Id6736ef4136590820078203d9fc31c20b8368093
Reviewed-on: https://chromium-review.googlesource.com/1177203
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583555}
1 file changed