Examine source code of Fiverr Notification Icon

{
  "manifest_version": 3,
  "name": "Fiverr Notification Icon in Title",
  "short_name": "Fiverr Notification Icon in Title",
  "version": "1.6.1",
  "description": "Turns the Fiverr tab icon red and plays an optional chime when a new message or notification arrives.",
  "author": "onepoordeveloper@gmail.com",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon-16.png",
      "128": "images/icon-128.png"
    }
  },
  "background": {
    "scripts": [
      "scripts/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{145e2028-4b50-47d7-b7df-9eae0683bc74}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "images/icon-16.png",
    "128": "images/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.fiverr.com/*"
      ],
      "js": [
        "scripts/chime.js",
        "scripts/contentscript.js"
      ],
      "run_at": "document_end",
      "all_frames": false
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "images/fiverr-red.png"
      ],
      "matches": [
        "https://www.fiverr.com/*"
      ]
    }
  ],
  "permissions": [
    "storage"
  ]
}