doc(Logout): add AvatarRadius documentation (dotnetcore#6806)

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Samples/Logouts.razor.cs

@@ -21,6 +21,14 @@ private static AttributeItem[] GetAttributes() =>
             DefaultValue = " — "
         },
         new()
+        {
+            Name = nameof(Logout.AvatarRadius),
+            Description = "登出组件当前用户头像圆角半径",
+            Type = "string",
+            ValueList = " — ",
+            DefaultValue = " — "
+        },
+        new()
         {
             Name = nameof(Logout.DisplayName),
             Description = "登出组件当前用户显示文字",