Examine source code of Youtube Comfortable Seek

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "default_locale": "en",
  "icons": {
    "48": "icons/youtube-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "youtube.js"
      ]
    }
  ]
}