Add simple app icon

writeas/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -41,13 +41,15 @@
       "scale" : "2x"
     },
     {
-      "idiom" : "mac",
       "size" : "512x512",
+      "idiom" : "mac",
+      "filename" : "w_ios.png",
       "scale" : "1x"
     },
     {
-      "idiom" : "mac",
       "size" : "512x512",
+      "idiom" : "mac",
+      "filename" : "w_ios_lg.png",
       "scale" : "2x"
     }
   ],