Examine source code of Rotterdam skyline

{
  "theme": {
    "images": {
      "theme_frame": "Rotterdamskyline1.jpg"
    },
    "colors": {
      "frame": "#5e0c0c",
      "tab_background_text": "#0b1036"
    }
  },
  "version": "2.0",
  "name": "Rotterdam skyline",
  "manifest_version": 2,
  "description": "Drawing of the skyline of Rotterdam (the Netherlands)"
}