Examine source code of Site Customizer

{
  "manifest_version" : 2 ,
  "name" : "Site Customizer",
  "version" : "1.0.1",
  "description" : "An extension that lets you easily customize the CSS of a website.",
  "browser_action" : {
    "default_title" : "Site Customizer\nCustomize this site?",
    "default_popup" : "popup.html",
    "default_icon" : {
      "16" : "logo/logo16.png",
      "32" : "logo/logo32.png",
      "48" : "logo/logo48.png",
      "64" : "logo/logo64.png",
      "128" : "logo/logo128.png"
    }
  },
  "icons" : {
    "16" : "logo/logo16.png",
    "32" : "logo/logo32.png",
    "48" : "logo/logo48.png",
    "64" : "logo/logo64.png",
    "128" : "logo/logo128.png"
  },
  "permissions" : [
    "activeTab" ,
    "clipboardWrite" 
  ],
  "content_scripts" : [
    {
      "matches" : [
        "<all_urls>" 
      ],
      "js" : [
        "/content_scripts/modifyCSS.js" 
      ]
    }
  ],
  "web_accessible_resources" : [
    "contextmenu.html",
    "css/contextmenu.css",
    "js/menuListener.js",
    "js/optionsListener.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{da0ef52f-95e9-487a-ab02-f4f35cfb7f59}"
    }
  }
}