Add lifetime hosted service to detect fully started ASP.NET Core

ElectronNET.API/App.cs

@@ -6,6 +6,7 @@ using System;
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.Extensions.Hosting;
 
 namespace ElectronNET.API
 {
@@ -352,6 +353,11 @@ namespace ElectronNET.API
 
         private event Action<bool> _accessibilitySupportChanged;
 
+        /// <summary>
+        /// Application host fully started.
+        /// </summary>
+        public bool IsReady { get; internal set; }
+
         /// <summary>
         /// A property that indicates the current application's name, which is the
         /// name in the application's `package.json` file.