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/admin-bundler/src/utils/config.ts

@@ -36,6 +36,7 @@ export async function getViteConfig(
         "react/jsx-runtime",
         "react-dom/client",
         "react-router-dom",
+        "react-i18next",
         "@medusajs/ui",
         "@medusajs/dashboard",
         "@medusajs/js-sdk",