Add spaceship exit component, enemy wave trigger, and update various scene properties

objects/entities/spaceship_exit.tscn

@@ -0,0 +1,14 @@
+[gd_scene load_steps=3 format=3 uid="uid://dkqa3q6j2gof4"]
+
+[ext_resource type="Script" uid="uid://ybmwls7hv8j3" path="res://scripts/components/spaceship_exit_component.gd" id="1_1cmfv"]
+
+[sub_resource type="RectangleShape2D" id="RectangleShape2D_njt46"]
+
+[node name="Spaceship exit" type="Area2D" node_paths=PackedStringArray("area2d")]
+collision_layer = 0
+collision_mask = 4
+script = ExtResource("1_1cmfv")
+area2d = NodePath(".")
+
+[node name="CollisionShape2D" type="CollisionShape2D" parent="."]
+shape = SubResource("RectangleShape2D_njt46")