implement test VCO redux state and actions

src/app/store.js

@@ -1,8 +1,10 @@
 import { configureStore } from '@reduxjs/toolkit';
 import counterReducer from '../features/counter/counterSlice';
+import timbreReducer from '../features/timbre/timbreSlice';
 
 export default configureStore({
-  reducer: {
-    counter: counterReducer,
-  },
+    reducer: {
+        counter: counterReducer,
+        timbre: timbreReducer,
+    },
 });