Examine source code of Dark Thunder

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#2f2f2f",
      "tab_background_text": "#d2d2d2"
    }
  },
  "version": "2.0",
  "name": "Dark Thunder",
  "manifest_version": 2,
  "description": "Simple dark theme for thunderbird, designed to complement linux mint 18 dark window themes\nLogo is:\nMozilla Thunderbird Logo 1\nby Mr-Logo (<a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/89c8dd26c98adc084a3608afb347fc0d80119f2b24fd5bf7beb34ada7a2c9a0e/https%3A//mr-logo.deviantart.com/art/Mozilla-Thunderbird-Logo-1-406375520\">https://mr-logo.deviantart.com/art/Mozilla-Thunderbird-Logo-1-406375520</a>)"
}