Bump i18n-js from 3.9.2 to 4.0.0

Bumps [i18n-js](https://github.com/fnando/i18n-js) from 3.9.2 to 4.0.0.
- [Release notes](https://github.com/fnando/i18n-js/releases)
- [Changelog](https://github.com/fnando/i18n-js/blob/main/CHANGELOG.md)
- [Commits](https://github.com/fnando/i18n-js/compare/v3.9.2...v4.0.0)

---
updated-dependencies:
- dependency-name: i18n-js
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

app/javascript/packs/application.js

@@ -40,6 +40,23 @@ import 'jquery-ui/themes/base/resizable.css'
 import 'jquery-ui/themes/base/selectable.css'
 import 'jquery-ui/themes/base/sortable.css'
 
+
+// I18n locales
+import { I18n } from "i18n-js";
+import locales from "../../../tmp/locales.json";
+
+// Fetch user locale from html#lang.
+// This value is being set on `app/views/layouts/application.html.erb` and
+// is inferred from `ACCEPT-LANGUAGE` header.
+const userLocale = document.documentElement.lang;
+
+export const i18n = new I18n();
+i18n.store(locales);
+i18n.defaultLocale = "en";
+i18n.enableFallback = true;
+i18n.locale = userLocale;
+window.I18n = i18n;
+
 // Routes
 import * as Routes from 'routes.js.erb';
 window.Routes = Routes;