Examine source code of Return to 1 Star

{
  "manifest_version": 3,
  "name": "__MSG_extName__",
  "version": "1.0.0",
  "description": "__MSG_extDescription__",
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "return-to-1-star@extension",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.google.com/maps/*",
        "*://www.google.de/maps/*",
        "*://www.google.at/maps/*",
        "*://www.google.ch/maps/*",
        "*://www.google.fr/maps/*",
        "*://www.google.nl/maps/*",
        "*://www.google.it/maps/*",
        "*://www.google.es/maps/*",
        "*://www.google.co.uk/maps/*",
        "*://www.google.be/maps/*",
        "*://maps.google.com/*",
        "*://maps.google.de/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_idle"
    }
  ]
}