message: Add placeholders for missing icon sizes
diff: {
  "images" : [
  + {
  + "idiom" : "iphone",
  + "size" : "20x20",
  + "scale" : "2x"
  + },
  + {
  + "idiom" : "iphone",
  + "size" : "20x20",
  + "scale" : "3x"
  + },
  {
  "idiom" : "iphone",
  "size" : "29x29",
  "size" : "60x60",
  "scale" : "3x"
  },
  + {
  + "idiom" : "ipad",
  + "size" : "20x20",
  + "scale" : "1x"
  + },
  + {
  + "idiom" : "ipad",
  + "size" : "20x20",
  + "scale" : "2x"
  + },
  {
  "idiom" : "ipad",
  "size" : "29x29",
  