Add 3D graphics prototype

[TimJentzsch]

Add a prototype for 3D graphics with a fixed camera angle.
It should be able to generate the hex tile map and encode the same information as the current 2D version.
It doesn't have to be pretty yet.

A good starting point for the hex tiles is probably this Bevy PR: bevyengine/bevy#6809
Hexagons can be created with a cylinder with a resolution of 6.
I think this code is only available on main yet, but we can probably vendor it for now.

[alice-i-cecile]

Done.