Examine source code of FreePDFapp

{
  "name": "FreePDFapp",
  "description": "FreePDFapp is a powerful PDF converter tool. Convert PDF to DOC and DOC to PDF with just a simple drag-and-drop",
  "version": "1.0.0",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "bg.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "images/icon16.png",
      "32": "images/icon32.png",
      "64": "images/icon64.png"
    }
  },
  "icons": {
    "16": "images/icon16.png",
    "32": "images/icon32.png",
    "64": "images/icon64.png",
    "128": "images/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b12d1baa-70b0-44b5-a7f9-1ed775ddc184}"
    }
  }
}