Emby server support

[marcus-downing]

I run Taiga and Emby Server on the same machine as my anime; and I watch it on other devices, like a tablet with the Emby app. It would be nice if Taiga could update based on the files streamed by Emby.

This is different from the existing issue for Emby support, which is focused on client side detection.

This may be difficult to achieve, since Emby Server is running as a background process rather than a local media player. It does have the ability to call webhooks, see below; can Taiga receive those?