Examine source code of SoundMarker

{
  "manifest_version": 2,
  "name": "SoundMarker",
  "version": "1.0",
  "description": "Place time-based markers on audio/video and return to them later. Markers saved per URL.",
  "icons": {},
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "soundmarker.js"
      ],
      "css": [
        "soundmarker.css"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6c2b8d5-2854-4c80-8c1d-8ab8270599be}"
    }
  }
}