Examine source code of Website Sleep Mode

{
  "manifest_version": 2,
  "name": "Website Sleep Mode",
  "version": "1.0",
  "description": "Automatically suspend inactive websites after a set period of time to save system resources and reduce bandwidth usage.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    },
    "default_title": "Website Sleep Mode"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3109d9be-b4cd-42f5-8808-dfb18ad6b289}"
    }
  }
}