Examine source code of X Profile Country Flag

{
  "manifest_version": 3,
  "name": "X Profile Country Flag",
  "version": "1.0.0",
  "description": "When you open a profile on X/Twitter, automatically reveals the 'Account based in' country (if X shows one) and puts a flag next to the person's name — no manual click on Joined needed.",
  "author": "you",
  "browser_specific_settings": {
    "gecko": {
      "id": "x-country-flag@example.local",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "*://twitter.com/*",
    "*://x.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://x.com/*"
      ],
      "js": [
        "countries.js",
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  }
}