doc: 更新示例

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Components/CustomerFilter.razor

@@ -1,3 +1,13 @@
 @inherits FilterBase
 
-<Select Items="@_items" @bind-Value="@_value" IsUseDefaultItemWhenValueIsNull="true" IsPopover="true"></Select>
+@if (IsHeaderRow)
+{
+    <Select Items="@_items" @bind-Value="@_value" IsUseDefaultItemWhenValueIsNull="true" IsPopover="true"
+            ShowLabel="false" SkipValidate="true" OnSelectedItemChanged="_ => OnFilterAsync()"></Select>
+}
+else
+{
+    <Select Items="@_items" @bind-Value="@_value" IsUseDefaultItemWhenValueIsNull="true" IsPopover="true"></Select>
+}
+
+