Examine source code of WhatsApp Web Focus Mode

{
  "manifest_version": 3,
  "name": "WhatsApp Web Focus Mode",
  "description": "Toggle sidebar visibility on WhatsApp Web.",
  "version": "1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "whatsapp-focus-mode@lakshay.dev",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://web.whatsapp.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ]
}