Examine source code of Volume Booster v

{
  "manifest_version": 2,
  "name": "Volume Booster",
  "version": "1.0",
  "description": "Boost the audio volume of the current tab.",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{18540c9b-9aaa-4271-a0f1-66cbb81e0403}"
    }
  }
}