Add sourcemap to min lib

Author: dhh

app/assets/javascripts/es-module-shims.js.map

@@ -41,7 +41,7 @@ class Engine < ::Rails::Engine
 
     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 )
+        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")
       end