Setting up chromecast functionality

## Problem description

I can't seem to get the chromecast functionality working. I'm using Airsonic Advanced 11.0 on Debian, behind a proxy (https, Let's Encrypt Certs, Nginx). As far as I understand a cast icon should appear in the webinterface (Chrome), near the volume controls, but its not there. How do I set this up? I had a look at the documentation, but it does not mention anything about setting this up. Tried using Airsonic directly (http) (without going through the proxy), but this did not work either. Could someone please tell me what the needed steps are to get this working? Thanks in advance!