Examine source code of Toggle designMode

{
  "manifest_version": 3,
  "name": "Toggle designMode",
  "description": "Easily toggle your browser's native design mode",
  "version": "1.1",
  "icons": {
    "16": "icons/edit_inactive.png",
    "32": "icons/edit_inactive.png",
    "48": "icons/logo.png",
    "128": "icons/logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "toggle-designmode@sergio9929.com"
    }
  },
  "action": {
    "default_title": "Design mode is not available"
  },
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}