Examine source code of Sudoku.com Enhanced

{
  "manifest_version": 2,
  "name": "Sudoku.com Enhanced",
  "version": "1.0",
  "description": "Small changes to Sudoku.com.  Keyboard shortcuts, dark mode, and more.",
  "icons": {
    "64": "icons/icon-64x64.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://sudoku.com/evil/",
        "https://sudoku.com/expert/",
        "https://sudoku.com/hard/",
        "https://sudoku.com/medium/",
        "https://sudoku.com/easy/",
        "https://sudoku.com/",
        "https://sudoku.com/killer/expert/",
        "https://sudoku.com/killer/hard/",
        "https://sudoku.com/killer/medium/",
        "https://sudoku.com/killer/easy/",
        "https://sudoku.com/killer/"
      ],
      "js": [
        "sudokuEnhanced.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{42d38904-316d-48b3-b699-6b26b4b9df2a}"
    }
  }
}