Update docs for the 4.0.0 release.

Closes #12865.

PiperOrigin-RevId: 352966184
diff --git a/scripts/docs/doc_versions.bzl b/scripts/docs/doc_versions.bzl
index dd40f9e..02f1227 100644
--- a/scripts/docs/doc_versions.bzl
+++ b/scripts/docs/doc_versions.bzl
@@ -23,6 +23,10 @@
 
 DOC_VERSIONS = [
     {
+        "version": "4.0.0",
+        "sha256": "9d8e350a17b85624d8d78291d440e05f6ba8af493c1ccb846d0493579dade1b6",
+    },
+    {
         "version": "3.7.0",
         "sha256": "a534d37ef3867c92fae8692852f92820a34f63a5f9092bbbec6505c0f69d8094",
     },
diff --git a/site/_config.yml b/site/_config.yml
index f077cde..89dc745 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -16,11 +16,12 @@
 url: "https://docs.bazel.build" # used by jekyll-sitemap
 
 # Update this to the newest release for the default docs.bazel.build version.
-version: "3.7.0"
+version: "4.0.0"
 
 # This must be kept in sync with //scripts/docs:doc_versions.bzl
 doc_versions:
   - master
+  - 4.0.0
   - 3.7.0
   - 3.6.0
   - 3.5.1