Examine source code of Fix Youtube Volume

{
  "manifest_version": 2,
  "name": "Fix YouTube Volume",
  "version": "1.6",
  "description": "Fix YouTube's volume scaling to be logarithmic, making it scale with the way humans perceive audio.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "*://www.youtube.com/*"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "YouTube Volume Settings",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8873ba9b-0cbd-4e79-99a7-37f5942cdcba}"
    }
  }
}