Addition of TVHeadend

[YurNaybor]

I'd like to add TVHeadend, a streaming and recording server for television broadcasting services: https://tvheadend.org/

The image is provided by the linuxserver project: https://hub.docker.com/r/linuxserver/tvheadend

I use this service already in my ansible nas and I thought it might be useful for other users, too.

[Vinibo]

Hello @slangdaddy,
I'm also interested by the feature. With the recent activity of this project, I will give it a try in implementing it! Stay tuned!

[davestephens]

There is already a PR: #320. It needs flipping into a role, updating for Traefik 2.4 then it's pretty much good to go.