Examine source code of Unread Badge for Gmail™

{
  "manifest_version": 3,
  "name": "Unread Badge for Gmail™",
  "version": "1.0.1",
  "description": "Shows unread Gmail counts in the toolbar and opens Gmail in one click. Uses your existing Gmail session; no analytics or tracking.",
  "author": "Avihai Yaakov Shai",
  "homepage_url": "https://github.com/AvihaiShai",
  "browser_specific_settings": {
    "gecko": {
      "id": "unread-badge-for-gmail@avihaishai.github.io",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "websiteContent"
        ]
      }
    }
  },
  "permissions": [
    "alarms",
    "storage"
  ],
  "optional_host_permissions": [
    "https://mail.google.com/*"
  ],
  "background": {
    "scripts": [
      "parser.js",
      "background.js"
    ]
  },
  "action": {
    "default_title": "Gmail",
    "default_area": "navbar",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  }
}