Examine source code of Tab Sanity

{
  "manifest_version": 2,
  "name": "Tab Sanity",
  "version": "1.0",
  "description": "Limit the number of tabs that can be opened",
  "icons": {
    "48": "icons/tabsanity-48.png"
  },
  "options_ui": {
    "page": "options.html"
  },
  "background": {
    "scripts": [
      "defaults.js",
      "sanity.js"
    ]
  },
  "permissions": [
    "notifications",
    "storage"
  ]
}