doc: document client options godoc landing page
@@ -17,6 +17,11 @@ Package cloud is the root of the packages used to access Google Cloud
Services. See https://godoc.org/cloud.google.com/go for a full list
of sub-packages.
+Client Options
+
+All clients in sub-packages are configurable via client options. These options are
+described here: https://godoc.org/google.golang.org/api/option.
+
Authentication and Authorization
