Set up documentation

[ilancoulon]

Before/while becoming public, we should set up a nice documentation using Documenter.jl. There are already a lot of comments in the code that should allow the documentation to be quite full very quickly. We just need to write a few pages to explain the overall project (of course using some parts of the paper would be a good idea imo).

[3rdCore]

@PierreTsr

[3rdCore]

Some important documentation is still missing in some parts of the code. This will be treated in the following weeks.

Also it will be nice to have a working version of the documentation website automatically generated by documenter.jl