Examine source code of yewtu.be redirect

{
  "manifest_version": 2,
  "name": "yewtube",
  "version": "1.1",
  "description": "Automatically redirects all YouTube videos to yewtu.be",
  "icons": {
    "48": "icons/yewtube-48.png"
  },
  "permissions": [
    "webRequest",
    "https://*.youtube.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false,
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{161e2e75-435f-4afc-bfed-8aa280e06077}"
    }
  }
}