Examine source code of Newspaper Free

{
  "manifest_version": 2,
  "name": "Newspaper Free",
  "version": "1.2.2",
  "browser_specific_settings": {
    "gecko": {
      "id": "newspaperfree@example.com",
      "strict_min_version": "65.0"
    }
  },
  "description": "Articles on some German newspaper pages can be read for free.",
  "icons": {
    "48": "icons/newspaper.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.haz.de/*",
        "*://*.cz.de/*",
        "*://*.neuepresse.de/*",
        "*://*.goettinger-tageblatt.de/*",
        "*://*.waz-online.de/*",
        "*://*.paz-online.de/*",
        "*://*.kn-online.de/*",
        "*://*.ln-online.de/*",
        "*://*.ostsee-zeitung.de/*",
        "*://*.maz-online.de/*",
        "*://*.sn-online.de/*",
        "*://*.lvz.de/*",
        "*://*.dnn.de/*"
      ],
      "js": [
        "newspaperfree.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_end"
    }
  ]
}