Examine source code of Gotham

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#11151c",
      "tab_background_text": "#599cab"
    }
  },
  "version": "2.0",
  "name": "Gotham",
  "manifest_version": 2,
  "description": "<a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/4859282f26d1a0d86cf9d6d5bc75e7ffd276cd53683106678f7b6d6e852ceae9/https%3A//github.com/whatyouhide/gotham-contrib\">https://github.com/whatyouhide/gotham-contrib</a>"
}