Examine source code of World Clock

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#f0f0f0"
    }
  },
  "version": "2.0",
  "name": "World Clock",
  "manifest_version": 2,
  "description": "Stock credit: <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/53f81e032c76a4f31916f040a8081e9672816789c078be7ec1ac18df1431666d/https%3A//pixabay.com/en/users/PIRO4D-2707530/\">PIRO4D\n</a>"
}