Examine source code of LetterMarkd

{
  "manifest_version": 2,
  "name": "LetterMarkd",
  "version": "1.0.6",
  "description": "Letterboxd ratings and actions overlaid on any movie-related webpage.",
  "browser_specific_settings": {
    "gecko": {
      "id": "lettermarkd-app@labreo.com",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>",
    "https://letterboxd.com/*",
    "https://www.imdb.com/*",
    "https://www.boxofficemojo.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "exclude_matches": [
        "https://letterboxd.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}