Examine source code of XNfire

{
  "manifest_version": 2,
  "name": "XNfire",
  "description": "Firefox extension to warn browser users when the site they visit is an IDN domain",
  "homepage_url": "https://github.com/xn-twist/XNfire",
  "version": "1.0.0",
  "icons": {
    "64": "icons/icon.png"
  },
  "permissions": [
    "tabs",
    "*://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "idndetect.js"
      ]
    }
  ]
}