Examine source code of Page Sound Detector

{
  "manifest_version": 2,
  "name": "Page Sound Detector",
  "version": "1.0",
  "description": "Detects if any sound is being played on the current page using Web Audio API.",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/icon48.png",
    "default_popup": "popup.html",
    "default_title": "Page Sound Detector"
  },
  "icons": {
    "48": "icons/icon48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "detector.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c2353d8f-1f94-4c42-adb5-357ac740e8e3}"
    }
  }
}