Examine source code of letterboxd+

{
  "browser_specific_settings": {
    "gecko": {
      "id": "@letterboxd_plus"
    }
  },
  "version": "0.333",
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "permissions": [
    "webNavigation",
    "storage"
  ],
  "default_locale": "en",
  "name": "letterboxd+",
  "description": "random button, rating from other platforms",
  "content_scripts": [
    {
      "matches": [
        "*://*.letterboxd.com/*/list/*",
        "*://*.letterboxd.com/*/watchlist/*"
      ],
      "js": [
        "/utils.js",
        "/modules/random.js"
      ]
    }
  ],
  "manifest_version": 3,
  "icons": {
    "64": "icon.png"
  },
  "action": {
    "default_icon": {
      "64": "icon.png"
    },
    "default_popup": "options/options.html"
  }
}