cmd/golangorg: provide an example in -template help message

Change-Id: I33ad64c9202e95e5e1296cb1c5fadb7353bbac86
Reviewed-on: https://go-review.googlesource.com/c/website/+/199059
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: jeanbza

cmd/golangorg/main.go

@@ -65,7 +65,7 @@ var (
 
 	// layout control
 	showTimestamps = flag.Bool("timestamps", false, "show timestamps with directory listings")
-	templateDir    = flag.String("templates", "", "load templates/JS/CSS from disk in this directory")
+	templateDir    = flag.String("templates", "", "load templates/JS/CSS from disk in this directory (usually /path-to-website/content/static)")
 	showPlayground = flag.Bool("play", false, "enable playground")
 	declLinks      = flag.Bool("links", true, "link identifiers to their declarations")