Examine source code of SpaceDark

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#071336",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "SpaceDark",
  "manifest_version": 2,
  "description": "A simple dark space theme.\nImage credit to <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/820b093f0615dcc48aa1aee772bbfa265ec1d28e48cca640bb218acc0a97878e/https%3A//www.flickr.com/photos/zigzaglens/3566054676\">Anthony Citrano</a>"
}