Examine source code of MCMWatch

{
  "manifest_version": 2,
  "name": "MCMWatch",
  "version": "0.5",
  "description": "Checks for one card of mcm.",
  "icons": {
    "48": "icons/N.png"
  },
  "permissions": [
    "https://www.sandalas.de/projects/mcm/mcm_watch.php",
    "https://www.cardmarket.com/de/Magic/Products/Singles/*",
    "storage",
    "tabs",
    "notifications"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "background": {
    "scripts": [
      "js/jquery-3.4.1.min.js",
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/N.png",
    "default_popup": "popup.html"
  }
}