Examine source code of Footietracker

{
  "manifest_version": 2,
  "name": "Footietracker",
  "short_name": "Footietracker",
  "version": "1.9",
  "icons": {
    "16": "icons/logo_short_16.png",
    "48": "icons/logo_short_48.png",
    "128": "icons/logo_short_128.png"
  },
  "description": "Updates your Footietracker spreadsheet with your current Football Index portfolio",
  "author": "Sam Mckenzie",
  "homepage_url": "https://footietracker.com",
  "page_action": {
    "show_matches": [
      "https://*.footballindex.co.uk/*"
    ],
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/logo_short_16.png",
      "48": "icons/logo_short_48.png",
      "128": "icons/logo_short_128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js",
      "browser-polyfill.js"
    ]
  },
  "permissions": [
    "https://*.footballindex.co.uk/*",
    "https://*.footietracker.com/*",
    "cookies"
  ]
}