Examine source code of Letterboxd Util

{
  "manifest_version": 2,
  "name": "Letterboxd Downloader",
  "description": "leading you to sites that you can download movies.",
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "https://letterboxd.com/film/*"
      ],
      "js": [
        "script.js"
      ],
      "css": [
        "script.css"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "activeTab"
  ],
  "page_action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "icon.png",
    "32": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  }
}