Installation instruction for mixKernel

Authored by:Jérôme Mariette, Céline Brouard, Rémi Flamary and Nathalie Vialaneix inmixKernel 0.9-1.
Source:a-mixKernelInstallation.Rmd, Vignette:a-mixKernelInstallation.html. Last updated:2024-01-28.