feat: update demo.

demo/Ursa.Demo/Pages/TimelineDemo.axaml

@@ -39,6 +39,7 @@
                 <DataTemplate x:DataType="viewModels:TimelineItemViewModel">
                     <u:TimelineItem
                         Content="{Binding Content}"
+                        ItemType="{Binding ItemType}"
                         Time="{Binding Time}"
                         TimeFormat="{Binding TimeFormat}">
                         <u:TimelineItem.ContentTemplate>

demo/Ursa.Demo/ViewModels/TimelineDemoViewModel.cs

@@ -1,5 +1,6 @@
 using System;
 using CommunityToolkit.Mvvm.ComponentModel;
+using Ursa.Controls;
 
 namespace Ursa.Demo.ViewModels;
 
@@ -12,21 +13,24 @@ public class TimelineDemoViewModel: ObservableObject
             Time = DateTime.Now,
             TimeFormat = "yyyy-MM-dd HH:mm:ss",
             Description = "Item 1",
-            Content = "First"
+            Content = "First",
+            ItemType = TimelineItemType.Success,
         },
         new()
         {
             Time = DateTime.Now,
             TimeFormat = "HH:mm:ss",
             Description = "Item 2",
-            Content = "Content 2"
+            Content = "Content 2",
+            ItemType = TimelineItemType.Success,
         },
         new()
         {
             Time = DateTime.Now,
             TimeFormat = "HH:mm:ss",
             Description = "Item 3",
-            Content = "Content 3"
+            Content = "Content 3",
+            ItemType = TimelineItemType.Ongoing,
         },
         new()
         {
@@ -107,4 +111,5 @@ public class TimelineItemViewModel: ObservableObject
     public string? TimeFormat { get; set; }
     public string? Description { get; set; }    
     public string? Content { get; set; }
+    public TimelineItemType ItemType { get; set; }
 }