Gitlab-CI: correctly handle WARNING and NOTE in checks

Currently, check fails only if in an ERROR occurs especially because some warnings or notes occur because of reasons outside the scope of the package itself (dependency to 'qpdf' or curl issues like in https://gitlab.irstea.fr/HYCAR-Hydro/airgr/-/jobs/142218).

airGRiwrm now implements a new CI procedure that correcly handle WARNING in check by putting the job and the pipeline in failure state (See: https://gitlab.irstea.fr/in-wop/airGRiwrm/-/commits/master/.gitlab-ci.yml). This way of doing seems reasonable because of the CRAN's requirements which doesn't allow any WARNING in the check of a package submission.

This procedure can be implemented in airGR, especially the part using R tidyverse docker image hosted on the server hosted at INRAE Lyon.

A new concept "don't stop on failure" exists in Gitlab-CI (See: https://docs.gitlab.com/ee/ci/yaml/#allow_failure) that allows to continue a pipeline on a job failure and to display corresponding job and pipeline in an "orange warning state". That could be useful if we want to be aware of NOTEs in checks without setting all the check process in a red failure state.