Examine source code of Pomodoro Bell

{
  "manifest_version": 2,
  "name": "Pomodoro Bell",
  "version": "1.0",
  "description": "Plays a gentle bell every 25 minutes to support the Pomodoro technique.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ad64767d-180b-472d-b48e-2f88fb75c8c0}"
    }
  }
}