Add a(n animated) feature showcase

[C0rn3j]

I keep finding features I did not know the player had after YEARS of using it and even after going through a large portion of the codebase.

I didn't know synced lyrics were a thing until recently.

It would be nice if the README contained a section which nicely showcased all the features that can be shown visually.

The current screenshot is nice, but it is far from encompassing everything, and it could simply be an animation of the player playing something, lyrics included - gotta be careful to pick copyright free lyrics there; and more.

We could keep the current screenshot format/size and just make it animated + rotate/slide to other screens with other features as needed, i.e. to show the web radio functionality.

[Solarunit]

Yeah! Tauon is actually very customizable.

It could be just gif demos with:

• various views options
• radio view
• showcase view with visualisation
• search demo
• drag-and-drop tracks/playlist/files demo
• queue demo
• themes demo
• etc