fix(docs): keep header 'Why goflow' link, hide from sidebar

Author: vnykmshr

docs/content/docs/building-goflow.md

@@ -1,6 +1,6 @@
 ---
 title: "Why goflow"
-weight: 0
+bookHidden: true
 ---
 
 # Building Concurrent Systems in Go

docs/hugo.toml

@@ -33,6 +33,10 @@ theme = 'hugo-book'
     name = "GitHub"
     url = "https://github.com/vnykmshr/goflow"
     weight = 10
+  [[menu.before]]
+    name = "Why goflow"
+    url = "/docs/building-goflow/"
+    weight = 15
   [[menu.before]]
     name = "API Docs"
     url = "https://pkg.go.dev/github.com/vnykmshr/goflow"