feat: add new Toast.

src/Ursa/Controls/Toast/IToast.cs

@@ -0,0 +1,38 @@
+using Avalonia.Controls.Notifications;
+using Avalonia.Metadata;
+
+namespace Ursa.Controls;
+
+/// <summary>
+/// Represents a toast that can be shown in a window or by the host operating system.
+/// </summary>
+[NotClientImplementable]
+public interface IToast
+{
+
+    /// <summary>
+    /// Gets the toast message.
+    /// </summary>
+    string? Content { get; }
+
+    /// <summary>
+    /// Gets the <see cref="NotificationType"/> of the toast.
+    /// </summary>
+    NotificationType Type { get; }
+
+    /// <summary>
+    /// Gets the expiration time of the toast after which it will automatically close.
+    /// If the value is <see cref="TimeSpan.Zero"/> then the toast will remain open until the user closes it.
+    /// </summary>
+    TimeSpan Expiration { get; }
+
+    /// <summary>
+    /// Gets an Action to be run when the toast is clicked.
+    /// </summary>
+    Action? OnClick { get; }
+
+    /// <summary>
+    /// Gets an Action to be run when the toast is closed.
+    /// </summary>
+    Action? OnClose { get; }
+}