Examine source code of Railway Dreams

{
  "theme": {
    "images": {
      "theme_frame": "BR52.png"
    },
    "colors": {
      "frame": "#e3e3e3",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Railway Dreams",
  "manifest_version": 2,
  "description": "German Steam Engine BR 52,\nfoto created in Raesfeld, Germany"
}