Add instakill condition to Stats and a Fall Limit Area

Use the FallLimitArea.tscn to visually set a height in the level that will trigger an instakill.

Closes: #173

game/src/Combat/Stats.gd

@@ -26,7 +26,12 @@ func _ready() -> void:
 func take_damage(hit: Hit) -> void:
 	if invulnerable:
 		return
-		
+
+	# Damages with value of -1 mean instakill
+	if hit.damage == -1:
+		emit_signal("health_depleted")
+		return
+
 	var old_health = health
 	health -= hit.damage
 	emit_signal("damage_taken")
@@ -58,8 +63,8 @@ func remove_modifier(id: int) -> void:
 
 func set_invulnerable_for_seconds(time: float) -> void:
 	invulnerable = true
-	
+
 	var timer := get_tree().create_timer(time)
 	yield(timer, "timeout")
-	
+
 	invulnerable = false

game/src/Objects/FallLimitArea.tscn

@@ -0,0 +1,12 @@
+[gd_scene load_steps=3 format=2]
+
+[ext_resource path="res://src/Combat/DamageSource.tscn" type="PackedScene" id=1]
+
+[sub_resource type="LineShape2D" id=1]
+
+[node name="FallLimitArea" instance=ExtResource( 1 )]
+position = Vector2( 0, -2.93628 )
+damage = -1
+
+[node name="CollisionShape2D" parent="." index="0"]
+shape = SubResource( 1 )