Examine source code of Skip the Envelope

{
  "name": "Skip the Envelope",
  "version": "2.2",
  "manifest_version": 2,
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://delivery.cardago.com/*",
        "*://www.paypal.com/gifts/claim/*",
        "*://www.vcdelivery.com/certificate/*"
      ],
      "js": [
        "skip.js"
      ]
    }
  ],
  "page_action": {
    "default_title": "Click to extract GC info.",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/skip_envelope16.png",
      "32": "images/skip_envelope32.png",
      "48": "images/skip_envelope48.png",
      "96": "images/skip_envelope96.png",
      "128": "images/skip_envelope128.png"
    }
  },
  "icons": {
    "16": "images/skip_envelope16.png",
    "32": "images/skip_envelope32.png",
    "48": "images/skip_envelope48.png",
    "96": "images/skip_envelope96.png",
    "128": "images/skip_envelope128.png"
  }
}