Examine source code of QRer

{
  "name": "Qrer",
  "version": "0.1.0",
  "description": "Displays a QR code for the current URL",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "images/qricon_128.png"
    }
  },
  "icons": {
    "128": "images/qricon_128.png"
  },
  "permissions": [
    "tabs"
  ]
}