Examine source code of acceptcookie

{
  "name": "acceptcookie",
  "version": "1.3.0",
  "manifest_version": 2,
  "description": "Automatically click accept cookie button",
  "icons": {
    "48": "icons/48.png"
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "https://stackoverflow.com/*",
        "https://*.stackexchange.com/*",
        "https://www.youtube.com/*"
      ],
      "run_at": "document_end",
      "js": [
        "page.js"
      ]
    }
  ]
}