Added Loop Points to Custom Levels Menu

I'm gonna be honest, I forgot about this one.
This updates the ResourceSetter for this menu's BGM from the old one to the new one so it can use the JSON and BGM formats.

Assets/Audio/BGM/CustomLevel.bgm

@@ -0,0 +1,10 @@
+{
+	"Normal": {
+		"source": "CustomLevel.mp3",
+		"loop": 4.8
+	},
+	"Hurry": {
+		"source": "CustomLevel.mp3",
+		"loop": 4.8
+	}
+}

Assets/Audio/BGM/CustomLevel.json

@@ -0,0 +1,5 @@
+{
+	"variations": {
+		"SMB1": {"source": "CustomLevel.bgm"}
+	}
+}