Added a minimal GUI based on Avalonia UI library for C#

DiscordBotGUI/Program.cs

@@ -0,0 +1,24 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.ApplicationLifetimes;
+
+using System;
+
+namespace DiscordBotGUI
+{
+    internal class Program
+    {
+        // Initialization code. Don't use any Avalonia, third-party APIs or any
+        // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
+        // yet and stuff might break.
+        [STAThread]
+        public static void Main(string[] args) => BuildAvaloniaApp()
+            .StartWithClassicDesktopLifetime(args);
+
+        // Avalonia configuration, don't remove; also used by visual designer.
+        public static AppBuilder BuildAvaloniaApp()
+            => AppBuilder.Configure<App>()
+                .UsePlatformDetect()
+                .LogToTrace();
+    }
+}