Prepare TunnelX for open-source release

AppTunnel/ViewModels/RelayCommand.cs

@@ -0,0 +1,23 @@
+using System.Windows.Input;
+
+namespace AppTunnel.ViewModels;
+
+public class RelayCommand : ICommand
+{
+    private readonly Action<object?> _execute;
+    private readonly Predicate<object?>? _canExecute;
+
+    public RelayCommand(Action<object?> execute, Predicate<object?>? canExecute = null)
+    {
+        _execute = execute;
+        _canExecute = canExecute;
+    }
+
+    public bool CanExecute(object? parameter) => _canExecute?.Invoke(parameter) ?? true;
+    public void Execute(object? parameter) => _execute(parameter);
+    public event EventHandler? CanExecuteChanged
+    {
+        add => CommandManager.RequerySuggested += value;
+        remove => CommandManager.RequerySuggested -= value;
+    }
+}