Examine source code of YouTubeSkip

{
  "manifest_version": 2,
  "name": "YouTubeSkip",
  "version": "0.2",
  "description": "Inject JavaScript in every youtube tab to press the skip button for you every time an ads starts.",
  "icons": {
    "96": "icons/96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.youtube.com/*"
      ],
      "js": [
        "youtubeskip.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e3d09891-f235-4802-9cf1-407778897c0a}"
    }
  }
}