Examine source code of Tab Sound Muter

{
  "manifest_version": 2,
  "name": "Tab Sound Muter",
  "version": "1.0",
  "description": "Automatically mutes sound in background tabs",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{603c3381-9b80-4c47-a4fb-838c7831dc29}"
    }
  }
}