Examine source code of Focus Window Blocker Advanced

{
  "manifest_version" : 2 ,
  "name" : "Focus Window Blocker Advanced",
  "version" : "1.3",
  "description" : "Block distracting domains with custom timers. Optimized for advanced users.",
  "browser_specific_settings": {
    "gecko": {
      "id": "focus-window-advanced@gmail.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions" : [
    "tabs" ,
    "storage" ,
    "activeTab" 
  ],
  "background" : {
    "scripts" : [
      "core.js" 
    ]
  },
  "browser_action" : {
    "default_popup" : "focus.html"
  }
}