Add new camera FixedView2dTopLeft and add a 2D ray casting example using it.

[CM-IV]

This PR adds a new 2D camera FixedView2dTopLeft that implements the Camera2d trait. It makes some assumptions though, see the docs in the code for that.

This PR also adds a 2D Ray Casting demo ported over from C Raylib using the DDA Algorithm. You can use it to implement rendering systems like the old Wolfenstein games.

Screencast_20260111_123523.webm

[sebcrozet]

That looks good, thank you! I modified the approach to make the FixedView2d camera configurable instead of needing a separate FixedView2dTopLeft struct.