Examine source code of Pr@All

{
  "manifest_version": 3,
  "name": "Pr@All",
  "version": "1.0.1",
  "description": "Simple extension to mention all members of the opened WhatsApp group.",
  "permissions": [
    "activeTab",
    "scripting"
  ],
  "icons": {
    "16": "images/icon-16.png",
    "32": "images/icon-32.png",
    "48": "images/icon-48.png",
    "128": "images/icon-128.png"
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon-16.png",
      "32": "images/icon-32.png",
      "48": "images/icon-48.png",
      "128": "images/icon-128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://web.whatsapp.com/"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "devVijay@Everyone"
    }
  }
}