Examine source code of HN Karma Display

{
  "manifest_version": 2,
  "name": "Hacker News Karma",
  "version": "1.2.2",
  "description": "Displays the karma of Hacker News commenters next to their names",
  "permissions": [
    "https://hacker-news.firebaseio.com/*",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://news.ycombinator.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "hn-karma-logo.svg",
    "48": "hn-karma-logo.svg",
    "128": "hn-karma-logo.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{f824fc49-fbc7-4466-b2a6-f63af9cc065f}"
    }
  }
}