Examine source code of sudoku.com shortcuts

{
  "manifest_version": 3,
  "name": "sudoku.com shortcuts",
  "version": "0.1.1",
  "description": "Additional keyboard shortcuts for sudoku.com",
  "content_scripts": [
    {
      "matches": [
        "https://sudoku.com/",
        "https://sudoku.com/easy/",
        "https://sudoku.com/medium/",
        "https://sudoku.com/hard/",
        "https://sudoku.com/expert/",
        "https://sudoku.com/evil/",
        "https://sudoku.com/extreme/"
      ],
      "js": [
        "main.js"
      ],
      "run_at": "document_start",
      "world": "MAIN"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@sudoku-shortcuts",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}