Add retina app icon for Apple TV

(cherry picked from commit aefb7c680e9c14ea93d61116bae46e87410449a4)

Apple-TV/Assets.xcassets/App Icon & Top Shelf Image.brandassets/App Icon - Small.imagestack/Back.imagestacklayer/Content.imageset/Contents.json

@@ -7,6 +7,7 @@
     },
     {
       "idiom" : "tv",
+      "filename" : "Icon-Background@2x.png",
       "scale" : "2x"
     }
   ],

Apple-TV/Assets.xcassets/App Icon & Top Shelf Image.brandassets/App Icon - Small.imagestack/Front.imagestacklayer/Content.imageset/Contents.json

@@ -7,6 +7,7 @@
     },
     {
       "idiom" : "tv",
+      "filename" : "Icon-Foreground@2x.png",
       "scale" : "2x"
     }
   ],