Examine source code of ytaddskip

{
  "manifest_version": 2,
  "name": "ytaddskip",
  "version": "1.0",
  "description": ".",
  "permissions": [
    "tabs",
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4ac491ae-1d42-4fb7-bf12-66eaa7f4f5d8}"
    }
  }
}