Examine source code of Freedium Redirects

{
  "manifest_version": 2,
  "name": "Freedium Redirector",
  "version": "1.0",
  "description": "Redirects Medium articles to Freedium mirror for free reading",
  "browser_specific_settings": {
    "gecko": {
      "id": "freedium-redirector@freedium.example",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://medium.com/*",
        "*://*.medium.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "48": "icon-48.png",
    "96": "icon-96.png"
  }
}