Examine source code of TF2 Trading Enhanced

{
  "manifest_version": 2,
  "name": "TF2 Trading Enhanced",
  "version": "1.0.5",
  "description": "Adds additional features to backpack and Steam.",
  "icons": {
    "16": "images/halloween_icon16.png",
    "128": "images/halloween_icon128.png"
  },
  "content_scripts": [
    {
      "js": [
        "js/library/jquery-3.1.0.min.js",
        "js/library/bootstrap.min.js",
        "js/init.js",
        "js/backpack.js",
        "js/outpost.js",
        "js/profile_page.js",
        "js/trade_offer.js",
        "js/content.js"
      ],
      "matches": [
        "*://backpack.tf/classifieds*",
        "*://www.tf2outpost.com/*",
        "*://steamcommunity.com/tradeoffer/*",
        "*://steamcommunity.com/*/tradeoffers/sent/",
        "*://steamcommunity.com/id/*",
        "*://steamcommunity.com/profiles/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "tf2tradingenhanced@yourdomain.com"
    }
  }
}