doc: add umi ui tip

package.json

@@ -6,6 +6,7 @@
   "scripts": {
     "analyze": "cross-env ANALYZE=1 umi build",
     "build": "umi build",
+    "ui":"umi ui",
     "deploy": "cross-env ANT_DESIGN_PRO_ONLY_DO_NOT_USE_IN_YOUR_PRODUCTION=site npm run site && npm run gh-pages",
     "docker-hub:build": "docker build  -f Dockerfile.hub -t  ant-design-pro ./",
     "docker-prod:build": "docker-compose -f ./docker/docker-compose.yml build",

src/pages/Welcome.tsx

 import React from 'react';
-import { Card, Typography } from 'antd';
+import { Card, Typography, Alert } from 'antd';
 import { PageHeaderWrapper } from '@ant-design/pro-layout';
 import { FormattedMessage } from 'umi-plugin-react/locale';
 
@@ -20,6 +20,16 @@ const CodePreview: React.FC<{}> = ({ children }) => (
 export default (): React.ReactNode => (
   <PageHeaderWrapper>
     <Card>
+      <Alert
+        message="umi ui 现已发布，欢迎使用 npm run ui 启动体验。"
+        type="success"
+        showIcon
+        banner
+        style={{
+          margin: -12,
+          marginBottom: 24,
+        }}
+      />
       <Typography.Text strong>
         <a target="_blank" rel="noopener noreferrer" href="https://pro.ant.design/docs/block">
           <FormattedMessage