add rolling saw

objects/enemy/rolling_saw.tscn

@@ -0,0 +1,25 @@
+[gd_scene load_steps=6 format=2]
+
+[ext_resource path="res://graphics/enemy/sawblade.png" type="Texture" id=1]
+[ext_resource path="res://objects/enemy/rolling_fiend.tscn" type="PackedScene" id=2]
+
+[sub_resource type="AtlasTexture" id=1]
+atlas = ExtResource( 1 )
+region = Rect2( 0, 0, 12, 12 )
+
+[sub_resource type="AtlasTexture" id=2]
+atlas = ExtResource( 1 )
+region = Rect2( 12, 0, 12, 12 )
+
+[sub_resource type="SpriteFrames" id=3]
+animations = [ {
+"frames": [ SubResource( 1 ), SubResource( 2 ) ],
+"loop": true,
+"name": "default",
+"speed": 20.0
+} ]
+
+[node name="RollingSaw" instance=ExtResource( 2 )]
+
+[node name="AnimatedSprite" parent="." index="0"]
+frames = SubResource( 3 )