Examine source code of Youtube Volume Scroll

{
  "name": "Youtube Volume Scroll",
  "short_name": "YoutubeVolumeScroll",
  "version": "3.4.1",
  "description": "Enable scrolling mousewheel to control volume on Youtube and Youtube Music",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*",
        "https://music.youtube.com/*",
        "https://www.youtube-nocookie.com/embed/*"
      ],
      "all_frames": true,
      "js": [
        "index.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "pageAccess.js"
      ],
      "matches": [
        "https://www.youtube.com/*",
        "https://music.youtube.com/*",
        "https://www.youtube-nocookie.com/*"
      ]
    }
  ],
  "icons": {
    "16": "icons/icon16x16.png",
    "32": "icons/icon32x32.png",
    "48": "icons/BigIcon48x48.png",
    "128": "icons/BigIcon128x128.png",
    "512": "icons/BigIcon512x512.png"
  },
  "action": {
    "default_popup": "popup/popup.html"
  },
  "options_ui": {
    "page": "popup/popup.html",
    "open_in_tab": false
  },
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "youtube-volume-scroll@github.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background-script.js"
    ]
  }
}