Examine source code of WallpaperWolf

{
  "manifest_version": 2,
  "name": "WallpaperWolf - UHD Wallpapers",
  "version": "1.1",
  "description": "Show a page action after a period of inactivity in your web browser. Show uhd wallpapers when the page action is clicked.",
  "homepage_url": "https://www.wallpaperwolf.com",
  "icons": {
    "48": "icons/wallpaperwolf-48.png"
  },
  "permissions": [
    "alarms",
    "tabs"
  ],
  "page_action": {
    "default_icon": "icons/wallpaperwolf-32.png",
    "default_title": "WallpaperWolf"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}