Support i18n.

redux/actions/app.js

@@ -0,0 +1,16 @@
+import { createSlice } from '@reduxjs/toolkit';
+
+const app = createSlice({
+  name: 'app',
+  initialState: { locale: 'en' },
+  reducers: {
+    updateApp(state, action) {
+      state = action.payload;
+      return state;
+    },
+  },
+});
+
+export const { updateApp } = app.actions;
+
+export default app.reducer;

redux/reducers.js

@@ -1,6 +1,7 @@
 import { combineReducers } from 'redux';
+import app from './actions/app';
 import user from './actions/user';
 import websites from './actions/websites';
 import queries from './actions/queries';
 
-export default combineReducers({ user, websites, queries });
+export default combineReducers({ app, user, websites, queries });