fix: @storybook/react/demo has been removed and a replacement compone…

…nt added

ref: storybookjs/storybook#17899

examples/v7-managed-react/.storybook/preview-head.html

@@ -1,4 +1,14 @@
 <style>
+.button {
+  border: 1px solid #eee;
+  border-radius: 3;
+  background-color: #FFFFFF;
+  cursor: pointer;
+  font-size: 15;
+  padding: 3px 10px;
+  margin: 10;
+}
+
 .my-button {
   cursor: pointer;
   height: 32px;

examples/v7-managed-react/src/Button.jsx

@@ -0,0 +1,7 @@
+import React from 'react';
+
+export const Button = ({ children, onClick }) => (
+  <button className='button' onClick={onClick} type="button">
+    {children}
+  </button>
+);

examples/v7-managed-react/src/Button.stories.jsx

@@ -1,5 +1,5 @@
 import React from 'react';
-import { Button } from '@storybook/react/demo';
+import { Button } from './Button';
 import { action } from '@storybook/addon-actions';
 
 import { isScreenshot } from 'storycap';

examples/v7-managed-react/src/Welcome.jsx

@@ -0,0 +1,5 @@
+export const Welcome = ({ showApp }) => (
+  <button type="button" onClick={showApp}>
+    Welcome
+  </button>
+);

examples/v7-managed-react/src/Welcome.stories.jsx

@@ -1,5 +1,5 @@
 import { linkTo } from '@storybook/addon-links';
-import { Welcome } from '@storybook/react/demo';
+import { Welcome } from './Welcome';
 
 export default {
   title: 'Welcome',

examples/v7-managed-react/src/WelcomeOverride.stories.jsx

@@ -1,5 +1,5 @@
 import { linkTo } from '@storybook/addon-links';
-import { Welcome } from '@storybook/react/demo';
+import { Welcome } from './Welcome';
 
 export default {
   title: 'Welcome Override',