Examine source code of Bitcoin Price Tracker

{
  "manifest_version": 2,
  "name": "Bitcoin Price",
  "version": "1.0",
  "description": "Shows Bitcoin price in USD.",
  "icons": {
    "48": "icons/btcprice-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/btcprice-16.png",
      "32": "icons/btcprice-32.png"
    }
  }
}