Examine source code of Dark Theme for Firefox

{
  "manifest_version": 2,
  "homepage_url": "https://www.turnoffthelights.com",
  "theme": {
    "colors": {
      "frame": "#333333",
      "tab_background_text": "#fff",
      "toolbar": "#333333",
      "toolbar_field": "#333333",
      "toolbar_field_text": "white",
      "toolbar_field_border": "#505050",
      "tab_line": "white",
      "popup": "#333333",
      "popup_text": "white",
      "popup_border": "gray",
      "ntp_background": "#333333",
      "ntp_text": "white"
    }
  },
  "name": "Dark theme for Firefox",
  "version": "1.0.2.1resigned1",
  "description": "A dark Firefox theme for your web browser. It's simple and coherent.",
  "author": "Stefan vd",
  "applications": {
    "gecko": {
      "id": "{1afaee19-8dde-4b0e-8c84-f46ca0f02f06}",
      "strict_min_version": "63.0"
    }
  }
}