Hyperrectangle plots with Makie

plot_3d_makie.jl

### Code

```julia
function makie_3d_plot(scene, data::Vector{IntervalBox{3, N}}, color=nothing) where N

    # plotting a single box in 3D doesn't work as expected
    @assert length(data) > 1

    positions = [Point3f0(mid(X)) for X in data]
    scales = [Vec3f0(diam.(X)) for X in data]
    
    local colors

    if color == nothing
        xs = Float32[x[1] for x in positions]
        ys = Float32[x[2] for x in positions]
        zs = Float32[x[3] for x in positions]
        
        minx, maxx = extrema(xs)
        miny, maxy = extrema(ys)
        minz, maxz = extrema(zs)

        colors = RGBA{Float32}[
            RGBA( (xs[i] - minx) / (maxx - minx),
                (ys[i] - miny) / (maxy - miny),
                (zs[i] - minz) / (maxz - minz), 
                0.5f0 )

                for i in 1:length(data)
            ];
    
    else
        colors = [color for X in data]
    end

    ## Makie plotting:
    #                          centre            widths
    #cube = Rect3D(Vec3f0(-0.5, -0.5, -0.5), Vec3f0(1, 1, 1))
    cube = Rect3D(Vec3f0(0.0, 0.0, 0.0), Vec3f0(5., 5., 5.))

    Makie.meshscatter!(scene, positions, marker=cube, scales=scales, color=colors, transparency=true)
    
end
```

### Example use: