Examine source code of Unshort.link

{
  "description": "Prevent short link services from tracking you",
  "manifest_version": 2,
  "name": "Unshort.link - Free Link unshorten services",
  "version": "1.6",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "storage"
  ],
  "author": "Simon Frey",
  "options_ui": {
    "page": "options.html"
  },
  "browser_action": {
    "default_icon": {
      "32": "icons/32.png",
      "64": "icons/64.png",
      "128": "icons/128.png"
    },
    "default_title": "Unshort.link"
  },
  "icons": {
    "32": "icons/32.png",
    "64": "icons/64.png",
    "128": "icons/128.png"
  },
  "homepage_url": "https://github.com/simonfrey/unshort.link",
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{953bc7fb-ace9-4aad-9bdd-13363e3fdaaf}"
    }
  }
}