Add GUI template

- Add AvaloniaUI GUI template to the project
- Add missing newline to the CLI output

HyperbolicDownloaderGUI/App.axaml.cs

@@ -0,0 +1,30 @@
+using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Markup.Xaml;
+
+using HyperbolicDownloaderGUI.ViewModels;
+using HyperbolicDownloaderGUI.Views;
+
+namespace HyperbolicDownloaderGUI
+{
+    public class App : Application
+    {
+        public override void Initialize()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+
+        public override void OnFrameworkInitializationCompleted()
+        {
+            if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+            {
+                desktop.MainWindow = new MainWindow
+                {
+                    DataContext = new MainWindowViewModel(),
+                };
+            }
+
+            base.OnFrameworkInitializationCompleted();
+        }
+    }
+}