Examine source code of HN Card

{
  "name": "HN Card",
  "version": "1.3",
  "description": "HN Card adds profile overlays to Hacker News usernames",
  "manifest_version": 2,
  "permissions": [
    "http://news.ycombinator.com/*",
    "https://news.ycombinator.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://news.ycombinator.com/*",
        "https://news.ycombinator.com/*"
      ],
      "css": [
        "css/drop.css",
        "css/hnprofile.css"
      ],
      "js": [
        "js/jquery.js",
        "js/drop.js",
        "js/md5.js",
        "js/hnprofile.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "img/*"
  ],
  "icons": {
    "16": "img/icon/icon16.png",
    "48": "img/icon/icon48.png",
    "128": "img/icon/icon128.png"
  }
}