Add default config in insert_into_file method

Author: Mateusz Michalski

lib/thor/actions/inject_into_file.rb

@@ -23,7 +23,11 @@ module Actions
     #
     def insert_into_file(destination, *args, &block)
       data = block_given? ? block : args.shift
-      config = args.shift
+      default_config = { after: "Rails::Initializer.run do |config|\n" }
+
+      config = (args.shift || default_config)
+      config.merge!(after: default_config[:after]) if (config.is_a?(Hash) && !config.key?(:after))
+
       action InjectIntoFile.new(self, destination, data, config)
     end
     alias_method :inject_into_file, :insert_into_file