add killzone and convert Tilemap to Tilelayer

scripts/killzone.gd

@@ -0,0 +1,11 @@
+extends Area2D
+
+@onready var timer: Timer = $Timer
+
+func _on_body_entered(_body: Node2D) -> void:
+	print("You died.")
+	timer.start()
+
+
+func _on_timer_timeout() -> void:
+	get_tree().reload_current_scene()