[Enhance][Bug fix] download songlist & new skill & API null recent

- Add `amane` and add support for `skill_amane`
- Add a parser for `songlist` to specify downloadable files
- Fix a bug that users with no recent scores cannot get `recent30` via API

latest version/database/init/singles.json

@@ -1216,5 +1216,41 @@
 		],
 		"orig_price": 100,
 		"price": 100
+	},
+	{
+		"name": "freemyself",
+		"items": [
+			{
+				"type": "single",
+				"id": "freemyself",
+				"is_available": true
+			},
+			{
+				"type": "core",
+				"amount": 1,
+				"id": "core_generic",
+				"is_available": true
+			}
+		],
+		"orig_price": 100,
+		"price": 100
+	},
+	{
+		"name": "cocorocosmetic",
+		"items": [
+			{
+				"type": "single",
+				"id": "cocorocosmetic",
+				"is_available": true
+			},
+			{
+				"type": "core",
+				"amount": 1,
+				"id": "core_generic",
+				"is_available": true
+			}
+		],
+		"orig_price": 100,
+		"price": 100
 	}
 ]