Examine source code of favicon-customizer

{
  "name": "favicon-customizer",
  "description": "This extension allows you to customize the favicon for a given url + optional page title match.",
  "version": "0.6",
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "favicon-customizer@muffinresearch.co.uk"
    }
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "options.html"
  }
}