merge of all libgdx-demos:
- https://github.com/libgdx/libgdx-demo-superjumper
- https://github.com/libgdx/libgdx-demo-cuboc
- https://github.com/libgdx/libgdx-demo-invaders
- https://github.com/libgdx/libgdx-demo-pax-britannica
- https://github.com/libgdx/libgdx-demo-vector-pinball
- https://github.com/libgdx/libgdx-demo-very-angry-robots
- https://github.com/libgdx/libgdx-demo-metagun
only for desktop