Examine source code of GMail New Tab Button

{
  "manifest_version": 3,
  "name": "GMail Button Extension",
  "version": "0.23",
  "description": "Displays GMail button on a toolbar with account selection",
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "contextMenus"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "64": "icons/icon64.png",
      "96": "icons/icon96.png",
      "128": "icons/icon128.png"
    },
    "default_title": "Gmail Quick Access (Right-click for account selection)",
    "default_area": "navbar"
  },
  "icons": {
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "64": "icons/icon64.png",
    "96": "icons/icon96.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "gmailbuttonextension@keepdev.com",
      "strict_min_version": "109.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "options_ui": {
    "page": "options.html"
  }
}