Add webpacker and use it for new_design

bin/webpack

@@ -0,0 +1,15 @@
+#!/usr/bin/env ruby
+
+ENV["RAILS_ENV"] ||= ENV["RACK_ENV"] || "development"
+ENV["NODE_ENV"]  ||= ENV["NODE_ENV"] || "development"
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+require "rubygems"
+require "bundler/setup"
+
+require "webpacker"
+require "webpacker/webpack_runner"
+Webpacker::WebpackRunner.run(ARGV)