doc: 更新骨架屏说明

Author: ArgoZhang

src/BootstrapBlazor.Server/Locales/en-US.json

@@ -686,7 +686,7 @@
     "TreeViewCheckedItemsTitle": "Get all selected nodes",
     "TreeViewCheckedItemsIntro": "Get all nodes by setting the <code>OnTreeItemChecked</code> callback delegate",
     "TreeViewShowSkeletonTitle": "Loading skeleton screen",
-    "TreeViewShowSkeletonIntro": "By setting <code>ShowSkeleton</code>, the component displays the skeleton screen when the data is loaded asynchronously",
+    "TreeViewShowSkeletonIntro": "When the component <code>Items</code> is <code>null</code>, set <code>ShowSkeleton=\"true\"</code> to display the skeleton screen when asynchronously loading data. Set <code>ShowSkeleton=\"false\"</code> to display the default loading animation.",
     "TreeViewShowSkeletonButtonText": "Asynchronous loading",
     "TreeViewShowSearchTitle": "Show search",
     "TreeViewShowSearchIntro": "By setting <code>ShowSearch</code> to display the search bar, and using the <code>OnSearchAsync</code> callback method to set the data source to refresh the page",

src/BootstrapBlazor.Server/Locales/zh-CN.json

@@ -686,7 +686,7 @@
     "TreeViewCheckedItemsTitle": "获取所有选中节点",
     "TreeViewCheckedItemsIntro": "通过设置 <code>OnTreeItemChecked</code> 回调委托获取所有节点",
     "TreeViewShowSkeletonTitle": "加载骨架屏",
-    "TreeViewShowSkeletonIntro": "通过设置 <code>ShowSkeleton</code> 使异步加载数据时组件显示骨架屏",
+    "TreeViewShowSkeletonIntro": "当组件 <code>Items</code> 为 <code>null</code> 时，通过设置 <code>ShowSkeleton=\"true\"</code> 使异步加载数据时组件显示骨架屏，设置 <code>ShowSkeleton=\"false\"</code> 时显示默认正在加载动画",
     "TreeViewShowSkeletonButtonText": "异步加载",
     "TreeViewShowSearchTitle": "显示搜索栏",
     "TreeViewShowSearchIntro": "通过设置 <code>ShowSearch</code> 显示搜索栏，通过 <code>OnSearchAsync</code> 回调方法设置数据源刷新页面即可",