turn Webpacker into a deprecation message wrapper

lib/shakapacker.rb

@@ -2,6 +2,7 @@
 require "active_support/core_ext/string/inquiry"
 require "active_support/logger"
 require "active_support/tagged_logging"
+require_relative "./shakapacker/webpacker"
 
 module Shakapacker
  extend self
@@ -45,7 +46,4 @@ def ensure_log_goes_to_stdout
 require "shakapacker/commands"
 require "shakapacker/dev_server"
 require "shakapacker/deprecation_helper"
-
 require "shakapacker/railtie" if defined?(Rails)
-
-Webpacker = Shakapacker

lib/shakapacker/webpacker.rb

@@ -0,0 +1,8 @@
+class Webpacker
+ def self.method_missing(method_name, *args, &block)
+ puts "The Webpacker constant has been superseded by the Shakapacker constant. "\
+ "Please change all references to the Webpacker constant, such as Webpacker.#{method_name}, "\
+ "to their Shakpacker equivalent, such as Shakapacker.#{method_name}"
+ Shakapacker.send(method_name, *args, &block)
+ end
+end