Examine source code of Reader Mode

{
  "manifest_version": 3,
  "name": "ReadEase",
  "version": "1.0",
  "description": "Transform any page into a dyslexia-friendly reading mode with one click",
  "permissions": [
    "activeTab",
    "scripting",
    "storage"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fc470ab4-4a95-32ea-a3a4-e5b2fefc64c9}",
      "strict_min_version": "109.0"
    }
  }
}