Examine source code of Previous Tab Switch

{
  "browser_specific_settings": {
    "gecko": {
      "id": "previous-tab-switch@ascae.dev"
    }
  },
  "manifest_version": 3,
  "name": "Previous Tab Switch",
  "version": "1.3.3",
  "description": "Quickly switch between previous and current tab",
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "assets/images/switch.png",
      "32": "assets/images/switch.png",
      "48": "assets/images/switch.png",
      "128": "assets/images/switch.png"
    }
  },
  "commands": {
    "switch-tab": {
      "suggested_key": {
        "default": "Ctrl+Q",
        "mac": "MacCtrl+Q"
      },
      "description": "Switch between current and previous tab"
    }
  },
  "icons": {
    "16": "assets/images/switch.png",
    "32": "assets/images/switch.png",
    "48": "assets/images/switch.png",
    "128": "assets/images/switch.png"
  }
}