[roll third_party/pigweed] docs: Add builder viz to CI/CQ intro

This gives a section other pages can link to when referencing the
builder viz.

Original-Bug: b/302680656
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/175414

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: a96389142d68f63..3b86a16ef93997a
Roller-URL: https://ci.chromium.org/b/8767492909377911137
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: If92ac3d2bbfb086ef6778a9f7f233895d115ca25
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/175538
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index a963891..3b86a16 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit a96389142d68f634c8645b186d93573b391e3fff
+Subproject commit 3b86a16ef93997a7f71ecceebcb6a272b9c12419