adding exercies for steps 2-1 and 2-2

step2-02/exercise/src/components/TodoApp.tsx

@@ -0,0 +1,20 @@
+import React from 'react';
+import { Stack } from 'office-ui-fabric-react';
+import { TodoFooter } from './TodoFooter';
+import { TodoHeader } from './TodoHeader';
+import { TodoList } from './TodoList';
+import { Store } from '../store';
+
+export class TodoApp extends React.Component<any, Store> {
+  render() {
+    return (
+      <Stack horizontalAlign="center">
+        <Stack style={{ width: 400 }} gap={25}>
+          <TodoHeader />
+          <TodoList />
+          <TodoFooter />
+        </Stack>
+      </Stack>
+    );
+  }
+}