Examine source code of VisBug

{
  "name": "VisBug",
  "version": "0.4.6",
  "description": "Open source browser design tools",
  "manifest_version": 3,
  "icons": {
    "128": "icons/visbug.png"
  },
  "permissions": [
    "activeTab",
    "contextMenus",
    "scripting",
    "storage"
  ],
  "background": {
    "scripts": [
      "visbug.js"
    ],
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{50864413-c4c8-43b0-80b8-982c4a368ac9}",
      "strict_min_version": "124.0"
    }
  },
  "action": {
    "default_title": "Click or press Alt+Shift+D to launch VisBug",
    "default_icon": {
      "128": "icons/visbug.png"
    }
  },
  "web_accessible_resources": [
    {
      "resources": [
        "tuts/*.gif",
        "toolbar/*"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "windows": "Alt+Shift+D",
        "mac": "Alt+Shift+D",
        "chromeos": "Alt+Shift+D",
        "linux": "Alt+Shift+D"
      }
    }
  }
}