Examine source code of Token Thunderbird

{
  "theme": {
    "images": {
      "theme_frame": "thunderbirdheader.png"
    },
    "colors": {
      "frame": "#858181",
      "tab_background_text": "#918c8c"
    }
  },
  "version": "2.0",
  "name": "Token Thunderbird",
  "manifest_version": 2,
  "description": "Cred for the beautiful icon goes to <a href=\"https://outgoing.prod.mozaws.net/v1/f6929f7e80606bb2c7f2d38c3a1e09c8dc40b29174f56084fe567e417a72a428/http%3A//brsev.deviantart.com/\" rel=\"nofollow\">http://brsev.deviantart.com/</a>"
}