Examine source code of Link Unshorten

{
  "manifest_version": 2,
  "homepage_url": "https://timleland.com/link-unshorten-extension/",
  "name": "Link Unshorten",
  "version": "0.0.98",
  "icons": {
    "16": "img/icons/icon-16.png",
    "48": "img/icons/icon-48.png",
    "128": "img/icons/icon-128.png"
  },
  "description": "Easily Unshorten any Url!",
  "browser_action": {
    "default_title": "Link Unshortener",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "img/on16.png",
      "32": "img/on32.png"
    }
  },
  "background": {
    "scripts": [
      "js/bootstrap.js",
      "js/storage.js",
      "js/badge.js",
      "js/background.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ]
}