Add polyfill for fetch

app/frontend/application.js

@@ -3,10 +3,14 @@
 // a relevant structure within app/javascript and only use these pack files to reference
 // that code so it'll be compiled.
 require.context("govuk-frontend/govuk/assets")
+
+// Polyfills for IE
 import "core-js/features/promise"
+import "unfetch/polyfill"
+//
 
 import "./styles/application.scss"
-import "./controllers"
+// import "./controllers"
 import "@hotwired/turbo-rails"
 import { initAll } from "govuk-frontend"
 

package.json

@@ -27,6 +27,7 @@
     "sass": "^1.49.9",
     "sass-loader": "^12.6.0",
     "stimulus": "^3.0.0",
+    "unfetch": "^4.2.0",
     "webpack": "^5.70.0",
     "webpack-cli": "^4.9.2",
     "webpack-remove-empty-scripts": "^0.7.3"

yarn.lock

@@ -2592,6 +2592,11 @@ to-regex-range@^5.0.1:
   dependencies:
     is-number "^7.0.0"
 
+unfetch@^4.2.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/unfetch/-/unfetch-4.2.0.tgz#7e21b0ef7d363d8d9af0fb929a5555f6ef97a3be"
+  integrity sha512-F9p7yYCn6cIW9El1zi0HI6vqpeIvBsr3dSuRO6Xuppb1u5rXpCPmMvLSyECLhybr9isec8Ohl0hPekMVrEinDA==
+
 unicode-canonical-property-names-ecmascript@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-2.0.0.tgz#301acdc525631670d39f6146e0e77ff6bbdebddc"