feat: introducing DateTimePicker.

demo/Ursa.Demo/Pages/DateTimePickerDemo.axaml

@@ -0,0 +1,12 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:u="https://irihi.tech/ursa"
+             mc:Ignorable="d" d:DesignWidth="800"
+             d:DesignHeight="450"
+             x:Class="Ursa.Demo.Pages.DateTimePickerDemo">
+    <StackPanel Margin="20" Spacing="">
+        <u:DateTimePicker Width="300" PanelFormat="hh mm ss tt"/>
+    </StackPanel>
+</UserControl>

demo/Ursa.Demo/Pages/DateTimePickerDemo.axaml.cs

@@ -0,0 +1,13 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace Ursa.Demo.Pages;
+
+public partial class DateTimePickerDemo : UserControl
+{
+    public DateTimePickerDemo()
+    {
+        InitializeComponent();
+    }
+}

demo/Ursa.Demo/ViewModels/DateTimePickerDemoViewModel.cs

@@ -0,0 +1,6 @@
+namespace Ursa.Demo.ViewModels;
+
+public class DateTimePickerDemoViewModel
+{
+    
+}

demo/Ursa.Demo/ViewModels/MainViewViewModel.cs

@@ -36,6 +36,7 @@ public class MainViewViewModel : ViewModelBase
             MenuKeys.MenuKeyClassInput => new ClassInputDemoViewModel(),
             MenuKeys.MenuKeyClock => new ClockDemoViewModel(),
             MenuKeys.MenuKeyDatePicker => new DatePickerDemoViewModel(),
+            MenuKeys.MenuKeyDateTimePicker => new DateTimePickerDemoViewModel(),
             MenuKeys.MenuKeyDialog => new DialogDemoViewModel(),
             MenuKeys.MenuKeyDivider => new DividerDemoViewModel(),
             MenuKeys.MenuKeyDisableContainer => new DisableContainerDemoViewModel(),

demo/Ursa.Demo/ViewModels/MenuViewModel.cs

@@ -21,6 +21,7 @@ public class MenuViewModel: ViewModelBase
             new() { MenuHeader = "Class Input", Key = MenuKeys.MenuKeyClassInput },
             new() { MenuHeader = "Clock", Key = MenuKeys.MenuKeyClock, Status = "Updated" },
             new() { MenuHeader = "Date Picker", Key = MenuKeys.MenuKeyDatePicker, Status = "New"},
+            new() { MenuHeader = "Date Time Picker", Key = MenuKeys.MenuKeyDateTimePicker, Status = "New"},
             new() { MenuHeader = "Dialog", Key = MenuKeys.MenuKeyDialog },
             new() { MenuHeader = "Disable Container", Key = MenuKeys.MenuKeyDisableContainer },
             new() { MenuHeader = "Divider", Key = MenuKeys.MenuKeyDivider },
@@ -71,6 +72,7 @@ public static class MenuKeys
     public const string MenuKeyClassInput = "Class Input";
     public const string MenuKeyClock = "Clock";
     public const string MenuKeyDatePicker = "DatePicker";
+    public const string MenuKeyDateTimePicker = "DateTimePicker";
     public const string MenuKeyDialog = "Dialog";
     public const string MenuKeyDivider = "Divider";
     public const string MenuKeyDisableContainer = "DisableContainer";