Examine source code of Tab Group by Domain

{
  "manifest_version": 2,
  "name": "Tab Group by Domain",
  "version": "1.0",
  "description": "Group tabs by their domain and access them via a dropdown menu, and move all tabs of a domain to a new window.",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "group.png",
      "48": "group.png",
      "128": "group.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "group.png",
    "48": "group.png",
    "128": "group.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6b4505b0-4a03-481b-b72b-9cda7b9e5739}"
    }
  }
}