Examine source code of Sleep Timer

{
  "manifest_version": 2,
  "name": "Sleep Timer",
  "version": "1.0",
  "description": "Alerts you when it's your scheduled bedtime.",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "notifications",
    "alarms",
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2778f7a4-44bc-481f-8447-3c86373a3597}"
    }
  }
}