Examine source code of Tab Breath Sound

{
  "manifest_version": 2,
  "name": "Tab Breath Sound",
  "version": "1.3",
  "description": "Play a very soft ambient sound when opening a new tab.",
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-breath-sound@amo.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}