Show active stream count in the Live TV guide

[llaforest]

When Jellyfin connects to an IPTV provider, the amount of different streams is limited and I think it would be useful information to show the users what streams are currently active.

For exemple, I have two concurrent streams available from my IPTV provider and around 40 users on my Jellyfin. If a user watches hockey in French, another watches the news, when a third user tries to watch hockey in English, it will fail.

With my feature, that third user will see the French stream is active and will be able to hop on if he can bear the commentators... :)

So I propose to add a badge next to the channel number that will appear when 1 or more users are watching that channel to show the users which streams they can use if their primary choice is not wokring.

I've implemented it and it's running on my own server at the moment. Change is small, ready to contribute with a formal PR if it's of interest.

[llaforest]

By the way, this will need a follow-up PR in androidTV and kodi later on