Examine source code of Prolific Sound Notification

{
  "manifest_version": 2,
  "name": "Prolific Sound Notification",
  "short_name": "ProlificNotify",
  "version": "1.6",
  "author": "Jesse Lover",
  "description": "Allows to receive sound notifications from new Prolific Surveys and to receive updates on new surveys faster than without extension.",
  "background": {
    "scripts": [
      "ExtPay.js",
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://extensionpay.com/*"
      ],
      "js": [
        "ExtPay.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "https://app.prolific.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "permissions": [
    "storage"
  ],
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{51fd8e25-e4d7-4da1-8a4b-c50f48af9421}"
    }
  }
}