Examine source code of Big Firefox Logo

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#ffffff",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Big Firefox Logo",
  "manifest_version": 2,
  "description": "This theme is taken from <a rel=\"nofollow\" href=\"https://addons.mozilla.org/en-US/firefox/addon/simplle-fox-logo/\">https://addons.mozilla.org/en-US/firefox/addon/simplle-fox-logo/</a> with small visual improvements for Firefox 57."
}