feat(admin-*,dashboard): add dashboard i18n extensions (#13763)

* virtual i18n module

* changeset

* fallback ns

fallback to the default "translation" ns if the key isnt found. Allows to use a single "useTranslation("customNs")" hook for both custom and medusa-provided keys

* simplify merges

* optional for backward compat

* fix HMR

* fix generated deepMerge

* test

packages/admin/dashboard/src/i18n/config.ts

@@ -1,7 +1,5 @@
 import { InitOptions } from "i18next"
 
-import translations from "./translations"
-
 export const defaultI18nOptions: InitOptions = {
   debug: process.env.NODE_ENV === "development",
   detection: {
@@ -11,9 +9,8 @@ export const defaultI18nOptions: InitOptions = {
     order: ["cookie", "localStorage", "header"],
   },
   fallbackLng: "en",
+  fallbackNS: "translation",
   interpolation: {
     escapeValue: false,
-  },
-  resources: translations,
-  supportedLngs: Object.keys(translations),
+  }
 }