Firebase hosting URL needs .html to display a page

I am trying to host a website at Google Firebase. The index.html is shown as (e.x.)app.firebase.com, but when I want to access a page like login.html I need to type app.firebase.com/login.html, just app.fire-base.com/login doesn't work. How would I achieve this for every .html file in the directory (public), do I need to configure the firebase.json? I read the docs but I could not find any information.

Here is my .json

 {
      "hosting": {
        "public": "public",
        "signin": "/signin.html"

      }
    }