Examine source code of Play-Sudoku

{
  "manifest_version": 2,
  "name": "Sudoku",
  "version": "1.0",
  "description": "Play sudoku in the browser",
  "icons": {
    "452": "icons/sudoku.png"
  },
  "browser_action": {
    "default_icon": "icons/sudoku.png",
    "default_title": "Sudoku",
    "default_popup": "public/index.html"
  }
}