Examine source code of youtube-seconds

{
  "manifest_version": 2,
  "name": "youtube-seconds",
  "version": "1.1",
  "description": "youtube-seconds is an extension with which you can forward or backward seek 2s with arrow keys or 10s with shift+arrow-keys. Original Code by https://github.com/vdegenne. Icon by freepik.com > Dighital",
  "icons": {
    "48": "double-arrow_3301627.png",
    "96": "double-arrow_3301627_96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7a38d782-986b-4c79-a80b-89ad9c4dfa83}"
    }
  }
}