Added title screen and onboarding prompt

scenes/title_screen.gd

@@ -0,0 +1,14 @@
+extends CanvasLayer
+
+func _ready():
+	get_tree().paused = true
+
+func _unhandled_input(event):
+	if event is InputEventKey and event.pressed and not event.echo:
+		if event.keycode == KEY_SPACE or event.keycode == KEY_ENTER:
+			_start()
+
+func _start():
+	get_tree().paused = false
+	EventBus.game_started.emit()
+	queue_free()