docs: fix

Author: phphe

docs/v1/guide.md

@@ -123,7 +123,7 @@ The outer div is called `nodeBox`, don't modify its `padding-left, padding-right
 
 ```tsx{4-7,9}
 renderNodeBox: ({ stat, attrs, isPlaceholder }) => (
-  <div {...attrs}>
+  <div {...attrs} key={attrs.key}>
     {isPlaceholder ? (
       <div
         className="he-tree-drag-placeholder"

docs/zh/v1/guide.md

@@ -125,7 +125,7 @@ export default function App() {
 
 ```tsx{4-7,9}
 renderNodeBox: ({ stat, attrs, isPlaceholder }) => (
-  <div {...attrs}>
+  <div {...attrs} key={attrs.key}>
     {isPlaceholder ? (
       <div
         className="he-tree-drag-placeholder"

src/pages/customize_placeholder_and_node_box.tsx

@@ -11,7 +11,7 @@ export default function BasePage() {
     dataType: 'flat',
     onChange: setdata,
     renderNodeBox: ({ stat, attrs, isPlaceholder }) => (
-      <div {...attrs}>
+      <div {...attrs} key={attrs.key}>
         {isPlaceholder ? <div className="he-tree-drag-placeholder">drop here</div>
           : <div className="mynode">{stat.node.name}</div>
         }