Examine source code of Quick Calendar

{
  "manifest_version": 2,
  "name": "Quick Calendar",
  "version": "1.0",
  "description": "View a simple calendar quickly",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{daad3c08-a79b-4eb2-9dad-c28eea6a82d6}"
    }
  }
}