Add another gym about scene switching

docs/gyms/gym09_scene_switching/gym09_minigame.tscn

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+[gd_scene format=3 uid="uid://p83ndnog4l2h"]
+
+[ext_resource type="Script" uid="uid://bpu7ehr2qjc1f" path="res://docs/gyms/gym09_scene_switching/gym09_minigame.gd" id="1_script"]
+
+[node name="Gym09Minigame" type="Control" unique_id=313626257]
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_script")
+
+[node name="VBoxContainer" type="VBoxContainer" parent="." unique_id=419254278]
+layout_mode = 1
+anchors_preset = 8
+anchor_left = 0.5
+anchor_top = 0.5
+anchor_right = 0.5
+anchor_bottom = 0.5
+offset_left = -150.0
+offset_top = -80.0
+offset_right = 150.0
+offset_bottom = 80.0
+grow_horizontal = 2
+grow_vertical = 2
+
+[node name="TitleLabel" type="Label" parent="VBoxContainer" unique_id=529708548]
+layout_mode = 2
+text = "MINIGAME"
+horizontal_alignment = 1
+
+[node name="CounterLabel" type="Label" parent="VBoxContainer" unique_id=1005168486]
+unique_name_in_owner = true
+layout_mode = 2
+text = "Presses remaining: 5"
+horizontal_alignment = 1
+
+[node name="Button" type="Button" parent="VBoxContainer" unique_id=211036225]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 4
+text = "Press Me! (0/5)"
+
+[connection signal="pressed" from="VBoxContainer/Button" to="." method="_on_button_pressed"]