Examine source code of Who Is Tab

{
  "description": "A basic Add-on to get Whois information for current tab url.",
  "manifest_version": 2,
  "name": "Who Is Tab",
  "version": "1.1resigned1",
  "homepage_url": "https://rakeshonweb.com",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "applications": {
    "gecko": {
      "id": "whoistab@rakeshonweb.com"
    }
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/icon-32.png",
    "theme_icons": [
      {
        "light": "icons/icon-32.png",
        "dark": "icons/icon-32.png",
        "size": 32
      }
    ],
    "default_title": "Who Is Tab",
    "default_popup": "popup/choose_beast.html"
  }
}