How to configure firebase.json to serve Sveltes app.html instead of index.html

I tried to rewrite the destination from index.html to app.html like in this anwser but somehow it's not working. In the picture below is my directory structure. Maybe I am using a wrong path and cant see it.

The contents of my firebase.json

{
  "hosting": {
    "public": "src",
    "ignore": ["firebase.json", "**/.*", "**/node_modules/**"]
  },
  "emulators": {
    "hosting": {
      "port": 8080
    },
    "ui": {
      "enabled": true
    }
  },
  "rewrites": [
    {
      "source": "**",
      "destination": "/app.html"
    }
  ]
}