Examine source code of YouTube Scroll Rewind

{
  "manifest_version": 2,
  "name": "YouTube Scroll Rewind",
  "version": "1.0",
  "description": "Control YouTube or other video time with mouse scroll when hovering over the video.",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_title": "YouTube Scroll Rewind",
    "default_icon": {
      "16": "images/icon-16.png",
      "48": "images/icon-48.png",
      "128": "images/icon-128.png"
    }
  },
  "icons": {
    "16": "images/icon-16.png",
    "48": "images/icon-48.png",
    "128": "images/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{021ca8b7-80ac-4ec8-8250-6288699ecc9a}"
    }
  }
}