Examine source code of Train Facts

{
  "manifest_version": 2,
  "name": "Train Facts",
  "version": "1.0",
  "description": "Get a random Train Fact with the simple Click of a button",
  "permissions": [
    "https://train-facts.pages.dev/train_facts.json"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "64": "icon64.png",
      "128": "icon128.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{5b01f298-4bbb-4c25-96ec-1ad42fc1b6a3}"
    }
  }
}