Add add_to_queue method to Spirc

[photovoltex]

Is your feature request related to a problem? Please describe.
Currently you need to use the api to add an item to the queue even when we are the active device. As the handling exists anyways for the dealer handling, we could now expose the option to the Spirc.

Describe the solution you'd like
Add a add_to_queue method to the Spirc. The item should probably be a SpotifyId. This should (as most other Spirc methods) only work when we are the active device.

[kingosticks]

This should (as most other Spirc methods) only work when we are the active device.

Are you 100% sold on this? It seems like a useful thing for the library to be able to do. Maybe a rethink on some of this belongs in a separate issue.

[photovoltex]

As it is only in the Spirc and currently we only execute SpircCommands when we are the active device, this seemed the logical conclusion to me.

But we could also rethink the current state and maybe implement something that could also handle the commands when we are not the active device. I'm completely open for ideas and solution :D