Examine source code of iOS 11

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#d9a66f",
      "tab_background_text": "#e4e1eb"
    }
  },
  "version": "2.0",
  "name": "iOS 11",
  "manifest_version": 2,
  "description": "Do you like the official wallpaper for iOS 11? Do you want it as your theme for Firefox? Then you've come to the right place!"
}