Examine source code of Simple Zoom -

{
  "manifest_version": 3,
  "name": "Simple Zoom -",
  "version": "1.0.0",
  "description": "Un bouton simple (-) pour dézoomer dans la barre d'URL.",
  "permissions": [
    "activeTab",
    "tabs",
    "theme"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_title": "Zoom arrière",
    "default_icon": {
      "16": "icons/minus-dark.svg",
      "32": "icons/minus-dark.svg"
    }
  },
  "icons": {
    "16": "icons/minus-dark.svg",
    "32": "icons/minus-dark.svg",
    "48": "icons/minus-dark.svg",
    "128": "icons/minus-dark.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "simplezoomout@extension.com"
    }
  }
}