Examine source code of WhatsApp Redirect

{
  "manifest_version": 2,
  "name": "WhatsApp Redirect",
  "version": "1.0",
  "description": "Redireciona links do WhatsApp para o WhatsApp Web.",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://api.whatsapp.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "whatsapp-redirect@example.com"
    }
  }
}