Examine source code of Sound Booster

{
  "manifest_version": 3,
  "name": "Sound Booster",
  "version": "1.0",
  "description": "Adjust audio volume up to 600%",
  "browser_specific_settings": {
    "gecko": {
      "id": "{5904b226-b7d4-4a61-b3cf-630591cc44d2}",
      "strict_min_version": "109.0"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png",
    "192": "icons/icon-192.png"
  },
  "permissions": [
    "storage",
    "scripting"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_icon": "icons/icon-32.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "popup.html"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}