Examine source code of Piano Master

{
  "manifest_version": 2,
  "name": "Piano Master",
  "version": "1.0",
  "description": "Play and record your favorite piano tunes on a virtual electric piano.",
  "homepage_url": "https://www.chromethemer.com/",
  "icons": {
    "48": "icons/wallpaperwolf-48.png"
  },
  "permissions": [
    "alarms",
    "tabs"
  ],
  "page_action": {
    "default_icon": "icons/wallpaperwolf-32.png",
    "default_title": "Piano Master"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}