Automatically generate docs.json when it's needed

.gitignore

@@ -5,6 +5,3 @@
 tmp
 public/assets
 public/fonts
-public/docs/**/*
-!public/docs/docs.json
-!public/docs/**/index.json

lib/app.rb

@@ -35,6 +35,9 @@ class App < Sinatra::Application
 
     set :csp, false
 
+    require 'docs'
+    Docs.generate_manifest
+
     Dir[docs_path, root.join(assets_prefix, '*/')].each do |path|
       sprockets.append_path(path)
     end

public/docs/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

public/docs/docs.json

@@ -1 +0,0 @@
-[]