feat: Add Card control and card demo with album images.

src/Avalonia/HandyControlDemo_Avalonia/Data/Model/CardModel.cs

@@ -0,0 +1,10 @@
+namespace HandyControlDemo.Data;
+
+public class CardModel
+{
+    public string? Header { get; set; }
+
+    public string? Content { get; set; }
+
+    public string? Footer { get; set; }
+}