docs: Add favicon to pigweed.dev

Tested by building the docs locally and verifying the favicon is shown.

Change-Id: I6f43ed4a78d16400759aa521f1d18c96b7405c2f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/109078
Pigweed-Auto-Submit: Ted Pudlik <tpudlik@google.com>
Reviewed-by: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/docs/BUILD.gn b/docs/BUILD.gn
index 55903b6..301ce2c 100644
--- a/docs/BUILD.gn
+++ b/docs/BUILD.gn
@@ -31,6 +31,7 @@
     # TODO(b/235348007): This should be in the pw_doc_gen target instead of
     # here.
     "_static/css/pigweed.css",
+    "_static/pw_logo.ico",
   ]
   sources = [
     "code_of_conduct.rst",
diff --git a/docs/_static/pw_logo.ico b/docs/_static/pw_logo.ico
new file mode 100644
index 0000000..545efa6
--- /dev/null
+++ b/docs/_static/pw_logo.ico
Binary files differ
diff --git a/docs/conf.py b/docs/conf.py
index 80598eb..3e243bc 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -73,6 +73,8 @@
 # If false, no module index is generated.
 html_domain_indices = True
 
+html_favicon = 'docs/_static/pw_logo.ico'
+
 # If false, no index is generated.
 html_use_index = True