Examine source code of Pnut Short Link Creator

{
  "manifest_version": 2,
  "name": "Pnut Short Link Creator",
  "description": "This extension will create a shortened url link for you.",
  "version": "1.0.1",
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "browser_action": {
    "default_icon": "images/icon48.png",
    "default_title": "PNUTS",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab",
    "https://pnut.co/pnutpost"
  ]
}