[roll third_party/pigweed] docs: Add Sphinx-design extension

- Add sphinx-design
  https://sphinx-design.readthedocs.io/en/furo-theme/
- Add doc writing references
- Update console keyboard shortcuts to use :kbd: directives

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/57331

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 420af4b4688268c..78789cd45a8a6a0
Roller-URL: https://ci.chromium.org/b/8838700842407633793
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8838700842407633793
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7cc582331b0afee0591c7e6bbc0b40ca654e9048
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/57344
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 420af4b..78789cd 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 420af4b4688268c17f49dcebf607edcdf6541487
+Subproject commit 78789cd45a8a6a0de905448b0a26b6f50d2aec7b