ft: improved npc spawning logic

evolve-die-repeat/shared/npc/npc2D.gd

@@ -4,6 +4,8 @@ class_name NPC2D
 @export var maxHealth: int = 0
 var health: int = maxHealth
 
+signal died
+
 # Called when the node enters the scene tree for the first time.
 func _ready() -> void:
 	spawn()
@@ -30,6 +32,7 @@ func feed(source ) -> void:
 	push_error("Function feed() not implemented.")
 	
 func die() -> void:
+	died.emit()
 	queue_free()
 	# TODO: should associate this class with a loot table (or equivalent), and can then implement logic for dying in parent class here.