Examine source code of xo_cross

{
  "manifest_version": 2,
  "name": "xo_cross",
  "version": "1.0",
  "description": "Remove the nyt crossword header so you can see.",
  "icons": {
    "48": "icons/xo.png"
  },
  "permissions": [
    "*://*.nytimes.com/crosswords/game/*",
    "Host permissions"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.nytimes.com/crosswords/game/*"
      ],
      "js": [
        "xo.js"
      ]
    }
  ]
}