Split the doc and use mkdocs

[thomaspoignant]

Motivation

Currently, the readme is a bit hard to read because there is too much information on a single page.

Requirements

I think we should split the readme into multiple files and create a mkdocs site to display it correctly. I think we should use the material theme which is really great. We could deploy this site as GitHub Pages.

[thomaspoignant]

@aftouh what do you think about that?