feat: add year button implementation.

src/Ursa/Controls/DateTimePicker/CalendarYearButton.cs

@@ -0,0 +1,46 @@
+using System.Diagnostics;
+using Avalonia.Controls;
+using Avalonia.Controls.Mixins;
+namespace Ursa.Controls;
+
+internal enum CalendarYearViewMode
+{
+    Month,
+    Year,
+    // The button represents ten year, with one year before and one year after, 12 in total. 
+    YearRange,
+} 
+public class CalendarYearButton: ContentControl
+{
+    static CalendarYearButton()
+    {
+        PressedMixin.Attach<CalendarYearButton>();
+    }
+    
+    internal int Year { get; private set; }
+    
+    internal int Month { get; private set; }
+    
+    internal int StartYear { get; private set; }
+    
+    internal int EndYear { get; private set; }
+    
+    internal CalendarYearViewMode Mode { get; private set; }
+
+    internal void SetValues(CalendarYearViewMode mode, DateTime contextDate, int? month = null, int? year = null, int? startYear = null, int? endYear = null)
+    {
+        Debug.Assert(!(month is null && year is null && startYear is null && endYear is null));
+        Mode = mode;
+        Month = month ?? 0;
+        Year = year ?? 0;
+        StartYear = startYear ?? 0;
+        EndYear = endYear ?? 0;
+        Content = Mode switch
+        {
+            CalendarYearViewMode.Month => DateTimeHelper.GetCurrentDateTimeFormatInfo().AbbreviatedMonthNames[Month],
+            CalendarYearViewMode.Year => Year.ToString(),
+            CalendarYearViewMode.YearRange => StartYear + "-" + EndYear,
+            _ => Content
+        };
+    }
+}