Examine source code of Urlsh

{
  "description": "Create short links on l.hihn.org",
  "manifest_version": 2,
  "name": "Urlsh",
  "version": "1.5.3",
  "homepage_url": "https://git.hihn.org/rain0r/ff-urlsh",
  "icons": {
    "48": "icons/icon.png"
  },
  "permissions": [
    "<all_urls>",
    "activeTab",
    "webRequest",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/icon.png",
    "theme_icons": [
      {
        "light": "icons/icon.png",
        "dark": "icons/icon.png",
        "size": 48
      }
    ],
    "default_title": "urlsh",
    "default_popup": "popup/default.html"
  },
  "background": {
    "scripts": [
      "browser-polyfill.min.js",
      "background_scripts/background.js"
    ]
  }
}