Add documentation

[KwikKill]

Type of Issue

• Bug
• Feature Request
• Documentation
• Other

Description

One of the main reason for this langate rewrite is the need for documentation. We will have 2 docs, one technical documentation as a mdbook example in the website backend and the user documentation in the insalan wiki.

CI also need to be auto-deploying doc.

[pixup1]

For the auto deployment, we can either copy deploy_docs.sh to this repo, or just update mappings.txt in the infra-insalan.fr repo (probably the better option).