Support for Cast Connect

[GodTamIt]

Describe the feature you'd like

Related to this issue: jellyfin/jellyfin-chromecast#603

Currently, when casting to an Android TV, it seems that Jellyfin resorts to having the TV act as a web cast receiver. The new Cast Connect SDK allows Android TVs to act as a native app receiver, so casting to it launches the Jellyfin app itself. In other words, casting almost behaves as a "deep link" into the native Jellyfin application itself.

YouTube would be a good example of an application that supports being a native Android TV receiver.

Understandably, this is a pretty large project. I've only ever seen applications implement this, but I don't know how painful or complex this would be.

[nielsvanvelzen]

Although I'm not against adding this. Right now it won't be trivial. We don't want proprietary libraries in the app and as far as I'm aware there is no open-source implementation of the cast SDK. Just the Google provided one that relies on Google Play services.