[NEW] Icon (#383)

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@RocketChat/ReactNative

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![image](https://user-images.githubusercontent.com/804994/43228416-d8af49d6-9037-11e8-8830-a1803932c7fd.png)

ios/RocketChatRN/Images.xcassets/AppIcon.appiconset/Contents.json

@@ -147,7 +147,7 @@
     {
       "size" : "1024x1024",
       "idiom" : "ios-marketing",
-      "filename" : "icon-1024.png",
+      "filename" : "icon-1024@1x.png",
       "scale" : "1x"
     }
   ],
@@ -155,4 +155,4 @@
     "version" : 1,
     "author" : "xcode"
   }
-}
+}