Dispatch WebView2 runtime toast notification on UI thread (#811)

Wino.Core.Domain/Interfaces/INotificationBuilder.cs

@@ -31,6 +31,11 @@ public interface INotificationBuilder
     /// <param name="account">Account that needs attention.</param>
     void CreateAttentionRequiredNotification(MailAccount account);
 
+    /// <summary>
+    /// Shows a notification when WebView2 runtime is unavailable.
+    /// </summary>
+    void CreateWebView2RuntimeMissingNotification();
+
     /// <summary>
     /// Creates a calendar reminder toast for the specified calendar item.
     /// </summary>

Wino.Core.Domain/Interfaces/IWebView2RuntimeValidatorService.cs

@@ -0,0 +1,12 @@
+using System.Threading.Tasks;
+
+namespace Wino.Core.Domain.Interfaces;
+
+public interface IWebView2RuntimeValidatorService
+{
+    /// <summary>
+    /// Validates whether WebView2 runtime is installed and available for use.
+    /// </summary>
+    Task<bool> IsRuntimeAvailableAsync();
+}
+