Add workflow for auto build and deployment of book

[cderv]

This PR is the last one about deploying our books automatically.

• ~It uses renv to manage packages and install them in the same state as local build~ Edit: it does not anymore - it uses a DESCRIPTION file.
  • I removed some packages installation from index.Rmd. A lot of package where missing installation anyway.
• workflow works the same as other books
  • It uses Makefile to build the book:
    • Only Gitbook version on PR to check it builds correctly
    • Gitbook and PDF (version with strip content) on commit to main
  • It will publish on bookdown.org directly using rsconnect package (only on push to main)
    • I have set up the ID and key in environment secret inside the repo, so it should work.

I am still unsure if it is best to use renv or DESCRIPTION + pak. The laster have the advantage to autoinstall sys dep on linux, and allows several explicit ways to provides dependency (like book deps for R chunks in Imports, packages required for creating reference with write_bib() in Suggests, package for deployement in Config/need/deploy for example). But the former have the advantage to lock versions (which could also be an inconvenient.)

Anyway, let's see if that build this way. If you prefere not to use renv, I'll make the switch to DESCRIPTION.

[cderv]

This is now working at last. I removed renv and went with a simple DESCRIPTION as in the cookbook. Dealing with system dependencies of some R dependencies of our direct dependencies is painful.

I let you have a look and gave feedback before merging.

After that we'll be able to more efficiently update chapters of the book and get the version online automatically. That will be better!