Examine source code of Mail Checker for Zoho

{
  "manifest_version": 2,
  "name": "Mail Checker for Zoho",
  "version": "1.1.0",
  "description": "Get instant notifications when new Zoho Mail arrives—right in your browser toolbar",
  "permissions": [
    "storage",
    "alarms",
    "notifications",
    "https://api.mailchecker.workers.dev/*"
  ],
  "browser_action": {
    "default_title": "Mail Checker for Zoho",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://api.mailchecker.workers.dev/extension-bridge*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "callback.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "zoho-mail-counter@extensions.zoho.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}