Add touch on-screen controller to be able to play demo on mobile

[AGulev]

Describe the content you'd like
That would be nice to add one of existing on-screen controllers into the example to be able to play it on mobile.

[aglitchman]

It's a great idea! Furthermore, it'll be implemented soon, i.e. it will be based on the mobile controls of the FPS shooter.

[ufgo]

Its would be great!