fixing up docs

docs/step2-07/exercise/src/index.tsx

@@ -1,20 +1,14 @@
 import React from 'react';
 import ReactDOM from 'react-dom';
 import { reducer } from './reducers';
-import { createStore, compose } from 'redux';
+import { createStore } from 'redux';
 import { Provider } from 'react-redux';
 import { TodoApp } from './components/TodoApp';
 import { actions } from './actions';
 import { initializeIcons } from '@uifabric/icons';
+import { composeWithDevTools } from 'redux-devtools-extension';
 
-/* Goop for making the Redux dev tool to work */
-declare var window: any;
-const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;
-function createStoreWithDevTool(reducer, initialStore) {
-  return createStore(reducer, initialStore, composeEnhancers());
-}
-
-const store = createStoreWithDevTool(reducer, {});
+const store = createStore(reducer, {}, composeWithDevTools());
 
 store.dispatch(actions.addTodo('hello'));
 store.dispatch(actions.addTodo('world'));