add image

fe/resource/default.res.json

 {
 	"groups": [
 		{
-			"keys": "bg_jpg,egret_icon_png,description_json,control_jpg,grid_jpg,logo_jpg",
+			"keys": "bg_jpg,egret_icon_png,description_json,control_jpg,grid_jpg,logo_jpg,mask_jpg",
 			"name": "preload"
 		}
 	],
@@ -35,6 +35,11 @@
 			"name": "logo_jpg",
 			"type": "image",
 			"url": "assets/logo.jpg"
+		},
+		{
+			"name": "mask_jpg",
+			"type": "image",
+			"url": "assets/mask.jpg"
 		}
 	]
 }
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