Examine source code of Cafi Certificado A3

{
  "manifest_version": 2,
  "name": "Cafi Certificado A3",
  "version": "1.0.0",
  "description": "Assinatura de Nota Fiscal com Certificado A3",
  "homepage_url": "https://app.cafi.com.br",
  "applications": {
    "gecko": {
      "id": "cafi@cafi.com.br"
    }
  },
  "icons": {
    "48": "icons/icon-48.png"
  },
  "permissions": [
    "nativeMessaging",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.cafi.com.br/*"
      ],
      "js": [
        "cafi.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/disabled.png",
    "default_title": "Cafi Certificado A3"
  }
}