Examine source code of Darkify-pages

{
  "manifest_version": 2,
  "name": "Darkify",
  "version": "1.0",
  "description": "Turn dark mode for all web pages",
  "homepage_url": "https://gitlab.com/stiko_/firefox-darkify",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "darkify.js"
      ]
    }
  ],
  "options_ui": {
    "page": "settings.html"
  },
  "permissions": [
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "first.ext@gmail.com"
    }
  }
}