Examine source code of Calm Sound Tab

{
  "manifest_version": 2,
  "name": "Calm Sound Tab",
  "version": "1.0",
  "description": "Play calming nature sounds on new tab.",
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "permissions": [],
  "web_accessible_resources": [
    "calm.mp3"
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8a86173c-0cf3-42a8-b883-a742f10f0b46}"
    }
  }
}