Use consistent style in "importmap.assets" initializer (#76)

Author: rmacklin

lib/importmap/engine.rb

@@ -39,11 +39,11 @@ class Engine < ::Rails::Engine
       end
     end
 
-    initializer "importmap.assets" do
-      if Rails.application.config.respond_to?(:assets)
-        Rails.application.config.assets.precompile += %w( es-module-shims.js es-module-shims.min.js es-module-shims.js.map )
-        Rails.application.config.assets.paths << Rails.root.join("app/javascript")
-        Rails.application.config.assets.paths << Rails.root.join("vendor/javascript")
+    initializer "importmap.assets" do |app|
+      if app.config.respond_to?(:assets)
+        app.config.assets.precompile += %w( es-module-shims.js es-module-shims.min.js es-module-shims.js.map )
+        app.config.assets.paths << Rails.root.join("app/javascript")
+        app.config.assets.paths << Rails.root.join("vendor/javascript")
       end
     end