Examine source code of Box Breathing

{
  "manifest_version": 3,
  "name": "Box Breathing",
  "version": "1.0.0",
  "description": "Guided box breathing exercise — inhale, hold, exhale, hold.",
  "action": {
    "default_popup": "popup.html",
    "default_title": "Box Breathing"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "fonts/*.woff2",
        "fonts.css"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "box-breathing@extension",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}