Examine source code of Tab Duplicator

{
  "manifest_version": 2,
  "name": "Tab Duplicator",
  "version": "1.1",
  "description": "Duplicate current tab with Ctrl+Shift+D",
  "icons": {
    "16": "icons/tabicon_16.png",
    "48": "icons/tabicon_48.png",
    "128": "icons/tabicon_128.png"
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Tab Duplicator"
  },
  "commands": {
    "duplicate-tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+D"
      },
      "description": "Duplicate Current Tab"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c984acce-78d2-42eb-a05e-77b46b48b28b}"
    }
  }
}