Examine source code of Twilee

{
  "manifest_version": 2,
  "name": "Twilee",
  "version": "1.4",
  "description": "Replaces words in Twitter posts with leetspeak alternatives",
  "browser_specific_settings": {
    "gecko": {
      "id": "twilee@example.com"
    }
  },
  "permissions": [
    "storage",
    "*://twitter.com/*",
    "*://x.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://x.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "browser_action": {
    "default_icon": "icon.png"
  },
  "web_accessible_resources": [
    "wordList.json",
    "letterWordMapping.json"
  ]
}