feat: update light theme.

demo/Ursa.Demo/Pages/PaginationDemo.axaml

@@ -16,7 +16,7 @@
         <TextBlock Text="{Binding #page.CurrentPage}" />
         <u:Pagination
             Name="page"
-            PageSizeOptions="{Binding PageSizes}"
+            PageSizeOptions="10, 20, 50, 100"
             TotalCount="600" />
     </StackPanel>
 </UserControl>

demo/Ursa.Demo/ViewModels/PaginationDemoViewModel.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using Avalonia.Collections;
 using CommunityToolkit.Mvvm.ComponentModel;