Examine source code of Send to WhatsApp

{
  "manifest_version": 2,
  "name": "Send to WhatsApp",
  "version": "1.0",
  "description": "Send selected text to WhatsApp Web",
  "permissions": [
    "contextMenus",
    "tabs",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_title": "Send to WhatsApp"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b0fa1801-e01b-4fa8-90cb-50643f708021}"
    }
  }
}