docs: Use <a> as example

docs/tutorial/desktop-environment-integration.md

@@ -329,11 +329,14 @@ app, you need to call `webContents.startDrag(item)` API on `ondragstart` event.
 
 In web page:
 
-```javascript
+```html
-document.getElementById('targetItem').ondragstart = (event) => {
+<a href="#" id="drag">item</a>
-  event.preventDefault()
+<script type="text/javascript" charset="utf-8">
-  ipcRenderer.send('ondragstart', '/path/to/item')
+  document.getElementById('drag').ondragstart = (event) => {
-}
+    event.preventDefault()
+    ipcRenderer.send('ondragstart', '/path/to/item')
+  }
+</script>
 ```
 
 In the main process: