game: add enemy modifier class

scenes/enemies/enemy_base.gd

@@ -7,6 +7,7 @@ extends CharacterBody2D
 @export var target_distance: float = 6.0
 @export var path_update_interval: float = 1.5
 @export var xp_dropped: float = 5.0
+var modifiers: Array[EnemyMod] = []
 
 @onready var target_cast: RayCast2D = $TargetCast
 @onready var animation_player: AnimationPlayer = $AnimationPlayer