Examine source code of Simple MP3 Player

{
  "manifest_version": 2,
  "name": "Simple MP3 Player",
  "version": "1.0",
  "description": "An add-on to listen to MP3 audio files.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{46546472-6003-457d-b451-943645335acf}"
    }
  }
}