Demo audio track selection

[ouchadam]

Problem

The player supports audio track selecting but it's not present in the demo.

Solution

To add the ability to switch audio tracks to the demo.

Test(s) added

nil tests around the demo code

Screenshots

Before	After

Paired with

@Dorvaryn

[Mecharyry]

LGTM 💯 I'm not concerned about pulling out too many UI components at this point, bigger battles 😄

[jszmltr]

Looks good to me ! 💯