Examine source code of YouTube-Speed-Controller

{
  "manifest_version": 2,
  "name": "ROTEM-YoutTube-Speed-Controller",
  "version": "1.0",
  "description": "Adds a red border to all webpages matching mozilla.org.",
  "icons": {
    "48": "border-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "borderify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "ytspeedster@ytspeedster.com"
    }
  }
}