added simple ui

Scenes/FPSLabel.cs

@@ -0,0 +1,11 @@
+using Godot;
+
+public partial class FPSLabel : Label
+{
+	bool ShowFPS = true;
+
+	// Called every frame. 'delta' is the elapsed time since the previous frame.
+	public override void _Process(double delta) {
+		Text = ShowFPS ? $"FPS: {Engine.GetFramesPerSecond()}" : "";
+	}
+}