Examine source code of Hackernews dark theme

{
  "manifest_version": 2,
  "name": "Hackernews dark theme",
  "version": "1.0",
  "description": "Nice dark theme for hackernews.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://news.ycombinator.com/*"
      ],
      "js": [
        "script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{588a8dce-2c6c-4842-929c-10add4011c08}"
    }
  }
}