Examine source code of Halloween GitHub Forever

{
  "manifest_version": 2,
  "name": "Halloween GitHub Forever",
  "version": "1.0",
  "description": "Changed GitHub contribution graph to halloween all year long.",
  "icons": {
    "48": "icons/pumpkin.jpg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://github.com/*"
      ],
      "js": [
        "graphTheme.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{aadf0927-5b86-45d6-b78b-b3ff6a6058ed}"
    }
  }
}