Examine source code of Link Expander

{
  "manifest_version": 2,
  "name": "Link Expander",
  "version": "1.0.5.3",
  "description": "Unmask shortened and tracking links safely. Enter a short URL to follow its redirects to the real destination with the final status code, or use the right-click menu on any link to preview where it goes.",
  "icons": {
    "32": "images/icon-32.png",
    "48": "images/icon-48.png",
    "64": "images/icon-64.png",
    "96": "images/icon-96.png",
    "128": "images/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b315c303-6547-43a4-94b6-08e45f65f368}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "contextMenus",
    "notifications",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "app/background.js"
    ]
  },
  "browser_action": {
    "default_title": "Link Expander",
    "default_popup": "app/popup.html",
    "default_icon": {
      "32": "images/icon-32.png",
      "48": "images/icon-48.png",
      "64": "images/icon-64.png"
    }
  }
}