Feature: Added WindowOpener class, which prevents having duplicate windows of the same type opened at the same time

Wox/Helper/WindowOpener.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Windows;
+
+namespace Wox.Helper
+{
+	public static class WindowOpener
+	{
+		public static T Open<T>(params object[] args) where T : Window
+		{
+			var window = Application.Current.Windows.OfType<Window>().FirstOrDefault(x => x.GetType() == typeof(T))
+						 ?? (T)Activator.CreateInstance(typeof(T), args);
+			window.Show();
+			window.Focus();
+			Application.Current.MainWindow.Hide();
+			
+			return (T)window;
+		}
+	}
+}