[roll third_party/pigweed] docs: Clarify scope for newcomers

Provides a little more clarity around what the docs currently help with
vs. the long-term vision.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/76921

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: f30bce8bf2513e9..79f3767c95beb36
Roller-URL: https://ci.chromium.org/b/8825767975005810609
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8825767975005810609
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: If8b08289e729e7a5d5117772fd2a7e9688962b4a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/77080
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 f30bce8..79f3767 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f30bce8bf2513e924f461da6f2e7d1f2620a89f3
+Subproject commit 79f3767c95beb362d51c2a7b589b926347e7dc28