Examine source code of whyEXT YouTube Subbar

{
  "manifest_version": 3,
  "name": "whyEXT YouTube Subbar",
  "version": "0.1.0",
  "description": "Enhanced horizontal subscriptions bar for YouTube.",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "action": {
    "default_title": "YouTube Subbar",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png"
    },
    "default_popup": "popup.html"
  },
  "options_page": "options.html",
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "https://www.youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "youtube-subbar@whyext.local",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  }
}