Added a pause menu

It was actually not that difficult surprisingly. Adding this was pretty
fun.

Scripts/PauseMenuContinueButton.cs

@@ -0,0 +1,9 @@
+using Godot;
+using System;
+
+public partial class PauseMenuContinueButton : Button {
+    public void _on_button_up() {
+        Globals.IsPaused = false;
+        GetNode<Control>("../..").QueueFree();
+    }
+}