Examine source code of Video Seek

{
  "manifest_version": 2,
  "name": "Video Seek",
  "version": "1.3.5",
  "description": "Allows you to seek through videos with the mouse wheel",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "html/popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.udemy.com/*",
        "*://www.youtube.com/*"
      ],
      "js": [
        "js/content.js",
        "js/options.js",
        "js/popup.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{782de6f0-66ad-415d-9959-51f761929f78}"
    }
  }
}