Feat: add toc to api doc (#5552)

### What problem does this PR solve?

the api doc is too long,  add a toc might be better

![CleanShot 2025-03-03 at 16 53
17](https://github.com/user-attachments/assets/9dfbc682-fdbf-4b37-8a01-87049db51f86)


### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

web/src/components/api-service/chat-overview-modal/api-content.tsx

 import ChatApiKeyModal from '../chat-api-key-modal';
 import { usePreviewChat } from '../hooks';
 import BackendServiceApi from './backend-service-api';
+import MarkdownToc from './markdown-toc';
 
 const ApiContent = ({
   id,
             </Flex>
           </Card>
         )}
+        <div style={{ position: 'relative' }}>
+          <MarkdownToc content={apiDoc} />
+        </div>
         <MarkdownPreview source={apiDoc}></MarkdownPreview>
       </Flex>
       {apiKeyVisible && (

web/src/components/api-service/chat-overview-modal/markdown-toc.tsx

+import { Anchor } from 'antd';
+import type { AnchorLinkItemProps } from 'antd/es/anchor/Anchor';
+import React, { useEffect, useState } from 'react';
+
+interface MarkdownTocProps {
+  content: string;
+}
+
+const MarkdownToc: React.FC<MarkdownTocProps> = ({ content }) => {
+  const [items, setItems] = useState<AnchorLinkItemProps[]>([]);
+
+  useEffect(() => {
+    const generateTocItems = () => {
+      const headings = document.querySelectorAll(
+        '.wmde-markdown h2, .wmde-markdown h3',
+      );
+      const tocItems: AnchorLinkItemProps[] = [];
+      let currentH2Item: AnchorLinkItemProps | null = null;
+
+      headings.forEach((heading) => {
+        const title = heading.textContent || '';
+        const id = heading.id;
+        const isH2 = heading.tagName.toLowerCase() === 'h2';
+
+        if (id && title) {
+          const item: AnchorLinkItemProps = {
+            key: id,
+            href: `#${id}`,
+            title,
+          };
+
+          if (isH2) {
+            currentH2Item = item;
+            tocItems.push(item);
+          } else {
+            if (currentH2Item) {
+              if (!currentH2Item.children) {
+                currentH2Item.children = [];
+              }
+              currentH2Item.children.push(item);
+            } else {
+              tocItems.push(item);
+            }
+          }
+        }
+      });
+
+      setItems(tocItems.slice(1));
+    };
+
+    setTimeout(generateTocItems, 100);
+  }, [content]);
+
+  return (
+    <div
+      className="markdown-toc"
+      style={{
+        position: 'fixed',
+        right: 20,
+        top: 100,
+        width: 200,
+        background: '#fff',
+        padding: '10px',
+        maxHeight: 'calc(100vh - 170px)',
+        overflowY: 'auto',
+        zIndex: 1000,
+      }}
+    >
+      <Anchor items={items} affix={false} />
+    </div>
+  );
+};
+
+export default MarkdownToc;