game: add enemy manager

scenes/managers/enemy_manager.gd

@@ -0,0 +1,24 @@
+class_name EnemyManager
+extends Node2D
+
+@export var max_enemies: int
+@export var spawn_rate: float
+@export var target: CollisionObject2D
+
+@onready var timer: Timer = $Timer
+
+var enemy_scene = preload("res://scenes/enemies/enemy.tscn")
+
+func _ready() -> void:
+	timer.wait_time = spawn_rate / 1
+	timer.start()
+
+
+func _on_timer_timeout() -> void:
+	var enemies = get_tree().get_nodes_in_group(GlobalConst.GROUP_ENEMY)
+	GlobalConst.sig_debug_stats_set.emit("enemy_count", "%s" % len(enemies))
+	if len(enemies) < max_enemies:
+		var new_enemy = enemy_scene.instantiate()
+		new_enemy.position = target.position + Vector2(50, 50)
+		new_enemy.target = target
+		add_child(new_enemy)