Examine source code of Font Detector

{
  "name": "Font Detector",
  "short_name": "Font Detector",
  "version": "1.2.2",
  "version_name": "v1.2.2",
  "description": "Detects font properties and styles",
  "icons": {
    "16": "assets/icons/font-detector-logo-16.png",
    "48": "assets/icons/font-detector-logo-48.png",
    "128": "assets/icons/font-detector-logo-128.png"
  },
  "permissions": [
    "scripting",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "js/background.min.js"
    ]
  },
  "manifest_version": 3,
  "action": {
    "default_icon": {
      "19": "assets/icons/font-detector-logo-19.png",
      "38": "assets/icons/font-detector-logo-38.png"
    }
  },
  "web_accessible_resources": [
    {
      "resources": [
        "assets/icons/font-detector-logo-38.png"
      ],
      "matches": [
        "*://*/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f234dd7a-5c1d-449c-c0ab-2a801824568f}"
    }
  }
}