Examine source code of Seterra extra

{
  "browser_specific_settings": {
    "gecko": {
      "id": "seterraextra@example.com"
    }
  },
  "name": "Seterra extra",
  "version": "3.1.6",
  "description": "Dark mode, no label, and more cool features for Seterra",
  "host_permissions": [
    "https://*.geoguessr.com/*"
  ],
  "permissions": [
    "activeTab",
    "storage"
  ],
  "manifest_version": 3,
  "icons": {
    "16": "images/icon16.png",
    "32": "images/icon32.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.geoguessr.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "action": {
    "default_popup": "popup.html"
  }
}