Modules: Makie.jl extension

[utkinis]

Make an extension module for visualising the data with GLMakie

• volumeslices should use the PostProcessing module to gather data to rank 0 and plot
• contour should call isosurface extraction and MPI gather from the PostProcessing module

[luraess]

Ideally this should also work with CairoMakie for running on servers.

[utkinis]

Ideally this should also work with CairoMakie for running on servers.

Good point, it's actually just a Makie extension, not GLMakie in particular =)