Examine source code of KGR Calculator

{
  "manifest_version": 2,
  "name": "KGR Calculator",
  "version": "1.0",
  "description": "Calculate Keyword Golden Ratio to find low-competition keywords for SEO",
  "browser_action": {
    "default_title": "KGR Calculator"
  },
  "options_page": "kgr.html",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "128": "icon.png"
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1859219b-ce11-4230-89f4-a21edda5cbdf}"
    }
  }
}