Define a New_UI feature for local testing

We've implemented a New_UI feature in Flipflop in tenejo, but want to
beging implementing UI changes in zizia directly.  This change allows
us to code and test against the feature (disabled or enabled) directly
in the engine.

config/features.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+Flipflop.configure do
+  feature :new_ui,
+          default: false,
+          description: "Show new UI features and workflows."
+end

lib/zizia/engine.rb

@@ -20,6 +20,10 @@ class Engine < ::Rails::Engine
       app.config.assets.precompile << %w[zizia/application.js zizia/application.css]
     end
 
+    initializer "load_features" do
+      Flipflop::FeatureLoader.current.append(self)
+    end
+
     initializer :append_migrations do |app|
       unless app.root.to_s.match root.to_s
         config.paths['db/migrate'].expanded.each do |expanded_path|