it works!

src/i18n/index.js

@@ -0,0 +1,19 @@
+import i18n from 'i18next';
+import { initReactI18next } from 'react-i18next';
+
+import leftSidebarEn from './locales/en/leftSidebar.json';
+
+i18n.use(initReactI18next).init({
+  lng: 'en',
+  fallbackLng: 'en',
+  debug: true,
+  resources: {
+    en: {
+      translations: leftSidebarEn,
+    },
+  },
+  ns: ['translations'],
+  defaultNS: 'translations',
+});
+
+export default i18n;