Examine source code of sgwpricecheck

{
  "manifest_version": 2,
  "name": "Goodwill eBay Price Checker",
  "version": "2.4",
  "description": "Right-click to check eBay prices for Goodwill items",
  "permissions": [
    "contextMenus",
    "activeTab",
    "*://*.shopgoodwill.com/*",
    "scripting"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a5134eeb-5a7f-4d9e-a001-96cbe4a7113d}"
    }
  }
}