Examine source code of Youtube Auto Shutdown

{
  "manifest_version": 2,
  "name": "Youtube Auto Shutdown",
  "version": "1.0",
  "description": "Shuts down the PC after Youtube video has finished playing",
  "icons": {
    "48": "icons/youtube_auto_shutdown.svg"
  },
  "permissions": [
    "nativeMessaging"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "youtube_auto_shutdown@sixshaman.org",
      "strict_min_version": "60.0"
    }
  },
  "background": {
    "scripts": [
      "js/youtube_auto_shutdown_background.js"
    ]
  },
  "page_action": {
    "browser_style": true,
    "default_icon": "icons/youtube_auto_shutdown.svg",
    "default_title": "Youtube Auto Shutdown",
    "default_popup": "popup/youtube_auto_shutdown_popup.html",
    "show_matches": [
      "*://*.youtube.com/watch*"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "js/youtube_auto_shutdown.js"
      ]
    }
  ]
}